Respiratory syncytial virus (RSV), also called human respiratory syncytial virus (hRSV) and human orthopneumovirus, is a common, contagious
virus
A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsk ...
that causes infections of the
respiratory tract. It is a
negative-sense, single-stranded RNA virus
Negative-strand RNA viruses (−ssRNA viruses) are a group of related viruses that have negative-sense, single-stranded genomes made of ribonucleic acid. They have genomes that act as complementary strands from which messenger RNA (mRNA) is sy ...
. Its name is derived from the large cells known as ''
syncytia
A syncytium (; plural syncytia; from Greek: σύν ''syn'' "together" and κύτος ''kytos'' "box, i.e. cell") or symplasm is a multinucleate cell which can result from multiple cell fusions of uninuclear cells (i.e., cells with a single nucleus) ...
'' that form when infected cells fuse.
RSV is the single most common cause of respiratory hospitalization in infants, and reinfection remains common in later life: it is a notable
pathogen
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
in all age groups. Infection rates are typically higher during the cold winter months, causing
bronchiolitis
Bronchiolitis is inflammation of the small airways in the lungs. Acute bronchiolitis is due to a viral infection usually affecting children younger than two years of age. Symptoms may include fever, cough, runny nose, wheezing, and breathing ...
in infants,
common colds in adults, and more serious respiratory illnesses such as
pneumonia
Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severi ...
in the elderly and
immunocompromised
Immunodeficiency, also known as immunocompromisation, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that a ...
.
RSV can cause outbreaks both in the community and in hospital settings. Following initial infection via the eyes or nose, the virus infects the
epithelial cells
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercell ...
of the upper and lower airway, causing inflammation, cell damage, and airway obstruction.
A variety of methods are available for viral detection and diagnosis of RSV including
antigen testing, molecular testing, and
viral culture
Viral culture is a laboratory technique in which samples of a virus are placed to different cell lines which the virus being tested for its ability to infect. If the cells show changes, known as cytopathic effects, then the culture is positive.
...
.
The main prevention measures include hand-washing and avoiding close contact with infected individuals;
prophylactic
Preventive healthcare, or prophylaxis, consists of measures taken for the purposes of disease prevention.Hugh R. Leavell and E. Gurney Clark as "the science and art of preventing disease, prolonging life, and promoting physical and mental hea ...
use of
palivizumab
Palivizumab, sold under the brand name Synagis, is a monoclonal antibody produced by recombinant DNA
Recombinant DNA (rDNA) molecules are DNA molecules formed by laboratory methods of genetic recombination (such as molecular cloning) that br ...
is also available to prevent RSV infection in high-risk infants. Currently, there is no vaccine against RSV, although many are under development.
Treatment for severe illness is primarily supportive, including
oxygen therapy and more advanced breathing support with
CPAP
Continuous positive airway pressure (CPAP) is a form of positive airway pressure (PAP) ventilation in which a constant level of pressure greater than atmospheric pressure is continuously applied to the upper respiratory tract of a person. The ap ...
or
nasal high flow oxygen, as required. In cases of severe
respiratory failure
Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise ...
,
intubation
Intubation (sometimes entubation) is a medical procedure involving the insertion of a tube into the body. Patients are generally anesthetized beforehand. Examples include tracheal intubation, and the balloon tamponade with a Sengstaken-Blake ...
and
mechanical ventilation
Mechanical ventilation, assisted ventilation or intermittent mandatory ventilation (IMV), is the medical term for using a machine called a ventilator to fully or partially provide artificial ventilation. Mechanical ventilation helps move a ...
may be required.
Ribavirin
Ribavirin, also known as tribavirin, is an antiviral medication used to treat RSV infection, hepatitis C and some viral hemorrhagic fevers. For hepatitis C, it is used in combination with other medications such as simeprevir, sofosbuvir, pe ...
is the only
antiviral
Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Unlike most antibiotics, antiviral drugs do no ...
medication currently licensed for the treatment of RSV in children, although its use remains controversial.
Signs and symptoms
RSV infection can present with a wide variety of signs and symptoms that range from mild
upper respiratory tract infection
An upper respiratory tract infection (URTI) is an illness caused by an acute infection, which involves the upper respiratory tract, including the nose, sinuses, pharynx, larynx or trachea. This commonly includes nasal obstruction, sore thro ...
s (URTI) to severe and potentially life-threatening
lower respiratory tract infection
Lower respiratory tract infection (LRTI) is a term often used as a synonym for pneumonia but can also be applied to other types of infection including lung abscess and acute bronchitis. Symptoms include shortness of breath, weakness, fever, cough ...
s (LRTI) requiring hospitalization and
mechanical ventilation
Mechanical ventilation, assisted ventilation or intermittent mandatory ventilation (IMV), is the medical term for using a machine called a ventilator to fully or partially provide artificial ventilation. Mechanical ventilation helps move a ...
.
While RSV can cause respiratory tract infections in people of all ages and is among the most common childhood infections, its presentation often varies between age groups and immune status.
Reinfection is common throughout life, but infants and the elderly remain at highest risk for symptomatic infection.
Children
Most children will experience at least one RSV infection by age 2.
Most childhood RSV infections are fairly self-limited with typical upper respiratory tract signs and symptoms, such as nasal congestion,
runny nose
Rhinorrhea, rhinorrhoea, or informally runny nose is the free discharge of a thin mucus fluid from the nose; it is a common condition. It is a common symptom of allergies ( hay fever) or certain viral infections, such as the common cold or COVI ...
, cough, and low-grade fever.
Inflammation of the nasal mucosa (
rhinitis
Rhinitis, also known as coryza, is irritation and inflammation of the mucous membrane inside the nose. Common symptoms are a stuffy nose, runny nose, sneezing, and post-nasal drip.
The inflammation is caused by viruses, bacteria, irrita ...
) and throat (
pharyngitis
Pharyngitis is inflammation of the back of the throat, known as the pharynx. It typically results in a sore throat and fever. Other symptoms may include a Rhinorrhea, runny nose, cough, headache, difficulty swallowing, swollen lymph nodes, and a ...
), as well as redness of the eyes (
conjunctival infection), may be seen on exam.
Approximately 15–50% of children will go on to develop more serious lower respiratory tracts infections, such as bronchiolitis,
viral pneumonia
Viral pneumonia is a pneumonia caused by a virus. Pneumonia is an infection that causes inflammation in one or both of the lungs. The pulmonary alveoli fill with fluid or pus making it difficult to breathe. Pneumonia can be caused by bacteria, vir ...
, or
croup.
Infants are at the highest risk of disease progression.
Bronchiolitis
Bronchiolitis is inflammation of the small airways in the lungs. Acute bronchiolitis is due to a viral infection usually affecting children younger than two years of age. Symptoms may include fever, cough, runny nose, wheezing, and breathing ...
is a common lower respiratory tract infection characterized by inflammation and obstruction of the small airways in the lungs.
While several viruses can cause bronchiolitis, RSV is responsible for about 70% of cases.
It usually presents with 2 to 4 days of runny nose and congestion followed by worsening cough, noisy breathing,
tachypnea
Tachypnea, also spelt tachypnoea, is a respiratory rate greater than normal, resulting in abnormally rapid and shallow breathing.
In adult humans at rest, any respiratory rate of 1220 per minute is considered clinically normal, with tachypnea b ...
(fast breathing), and
wheezing
A wheeze is a continuous, coarse, whistling sound produced in the respiratory airways during breathing. For wheezes to occur, some part of the respiratory tree must be narrowed or obstructed (for example narrowing of the lower respiratory tract ...
.
As infants work harder to breathe, they can also show signs of
respiratory distress
Shortness of breath (SOB), also medically known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing di ...
, such as subcostal
retractions (when the belly pulls under the ribcage), intercostal retractions (when the muscles between the ribs pull inward), grunting, and nasal flaring.
If the child has not been able to feed adequately, signs of
dehydration
In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...
may also be present.
Fever may be present, but high-grade fever is uncommon.
Crackles and wheezing can often be heard on
auscultation, and
oxygen saturation
Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen that is dissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium at the given temperature. It ca ...
levels may be decreased.
In very young infants under 6 weeks of age, and particularly in premature infants, signs of infection may be less specific. They may have minimal respiratory involvement. Instead, they may exhibit decreased activity, irritability, poor feeding, or breathing with difficulties. This can also be accompanied by
apneic spells, or brief pauses in breathing.
Adults
Reinfection with RSV remains common throughout life. Reinfection in adulthood often produces only mild to moderate symptoms indistinguishable from the
common cold or
sinus infection
Sinusitis, also known as rhinosinusitis, is inflammation of the mucous membranes that line the sinuses resulting in symptoms that may include thick nasal mucus, a plugged nose, and facial pain. Other signs and symptoms may include fever, headac ...
.
Infection may also be
asymptomatic. If present, symptoms are generally isolated to the upper respiratory tract: runny nose, sore throat, fever, and
malaise. In the vast majority of cases, nasal congestion precedes the development of cough.
In contrast to other upper respiratory infections, RSV is also more likely to cause new onset wheeze in adults.
Only about 25% of infected adults will progress to significant lower respiratory tract infection, such as
bronchitis
Bronchitis is inflammation of the bronchi (large and medium-sized airways) in the lungs that causes coughing. Bronchitis usually begins as an infection in the nose, ears, throat, or sinuses. The infection then makes its way down to the bronchi. ...
or
tracheobronchitis Tracheobronchitis is inflammation of the trachea and bronchi. It is characterised by a cough, fever, and purulent (containing pus) sputum and is therefore suggestive of pneumonia. It is classified as a respiratory tract infection.
Tracheobronchitis ...
.
While RSV very rarely causes severe disease in healthy adults, it can cause significant morbidity and mortality in the elderly and in those with underlying immune compromise or cardiopulmonary disease. Older adults have a similar presentation to younger adults but tend to have greater symptom severity with increased risk of lower respiratory tract involvement. In particular, the elderly are more likely to experience
pneumonia
Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severi ...
,
respiratory distress
Shortness of breath (SOB), also medically known as dyspnea (in AmE) or dyspnoea (in BrE), is an uncomfortable feeling of not being able to breathe well enough. The American Thoracic Society defines it as "a subjective experience of breathing di ...
, and death.
Immunocompromised
In both adults and children, those who are
immunocompromised
Immunodeficiency, also known as immunocompromisation, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors that a ...
are at an increased risk of severe infection with RSV. Infected individuals in this group are more likely to progress from upper to lower respiratory tract involvement and have prolonged
viral shedding
Viral shedding is the expulsion and release of virus progeny following successful reproduction during a host cell infection. Once replication has been completed and the host cell is exhausted of all resources in making viral progeny, the viruse ...
.
Symptom severity seems to be closely related to the extent of immune suppression. Those who have undergone
hematopoietic stem cell transplant
Hematopoietic stem-cell transplantation (HSCT) is the transplantation of multipotent hematopoietic stem cells, usually derived from bone marrow, peripheral blood, or umbilical cord blood in order to replicate inside of a patient and to pro ...
(HSCT), intensive
chemotherapy
Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs ( chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemothe ...
, and
lung transplant
Lung transplantation, or pulmonary transplantation, is a surgical procedure in which one or both lungs are replaced by lungs from a donor. Donor lungs can be retrieved from a living or deceased donor. A living donor can only donate one lung lobe. ...
are particularly susceptible.
Bone marrow transplant patients appear to be at highest risk, especially prior to marrow engraftment. In this group, RSV infection carries a nearly 80% risk of both pneumonia and death.
Complications
Cause
Risk factors
Risk factors for development of severe lower respiratory tract infection with RSV vary by population.
Virology
Taxonomy
RSV is a
negative-sense
In molecular biology and genetics, the sense of a nucleic acid molecule, particularly of a strand of DNA or RNA, refers to the nature of the roles of the strand and its complementarity (molecular biology), complement in specifying a sequence of am ...
, single-stranded
RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
virus.
The scientific name for this viral species is ''Human orthopneumovirus.'' This is synonymous with ''Human respiratory syncytial virus'' (hRSV), which is often shortened to just RSV. It belongs to the genus ''
Orthopneumovirus,'' family ''
Pneumoviridae
''Pneumoviridae'' (from Greek pneumo-, lung, -viridae, virus from Latin, poison, slimy liquid) is a family of negative-strand RNA viruses in the order '' Mononegavirales''. Humans, cattle, and rodents serve as natural hosts. Respiratory tract in ...
'', order ''
Mononegavirales
''Mononegavirales'' is an order of negative-strand RNA viruses which have nonsegmented genomes. Some common members of the order are Ebola virus, human respiratory syncytial virus, measles virus, mumps virus, Nipah virus, and rabies virus. A ...
''.
Its name comes from the fact that
F proteins on the surface of the virus cause neighboring cell membranes to merge, creating large multinucleated
syncytia
A syncytium (; plural syncytia; from Greek: σύν ''syn'' "together" and κύτος ''kytos'' "box, i.e. cell") or symplasm is a multinucleate cell which can result from multiple cell fusions of uninuclear cells (i.e., cells with a single nucleus) ...
.
Antigenic subtypes
RSV is divided into two antigenic subtypes, A and B, based on the reactivity of the F and G surface proteins to monoclonal antibodies.
The subtypes tend to circulate simultaneously within local epidemics, although subtype A tends to be more prevalent.
Generally, RSV subtype A (RSVA) is thought to be more virulent than RSV subtype B (RSVB), with higher viral loads and faster transmission time.
To date, 16 RSVA and 22 RSVB
clades have been identified.
Among RSVA, the GA1, GA2, GA5, and GA7 clades predominate; GA7 is found only in the United States.
Among RSVB, the BA clade predominates worldwide.
Genome
![595768](https://upload.wikimedia.org/wikipedia/commons/b/b8/595768.fig.001.jpg)
RSV has a
negative-sense
In molecular biology and genetics, the sense of a nucleic acid molecule, particularly of a strand of DNA or RNA, refers to the nature of the roles of the strand and its complementarity (molecular biology), complement in specifying a sequence of am ...
, single-stranded RNA genome.
The
genome
In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding g ...
is linear and approximately 15,000
nucleotide
Nucleotides are organic molecules consisting of a nucleoside and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecule ...
s in length.
It is non-segmented which means that, unlike
influenza, RSV cannot participate in the type of genetic
reassortment
Reassortment is the mixing of the genetic material of a species into new combinations in different individuals. Several different processes contribute to reassortment, including assortment of chromosomes, and chromosomal crossover. It is particul ...
and
antigenic shifts responsible for large
pandemics.
It has 10
gene
In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...
s encoding for 11 proteins.
The gene order is NS1-NS2-N-P-M-SH-G-F-M2-L, with the NS1 and NS2 gene serving as nonstructural promoter genes.
Structure and proteins
![Human Respiratory Syncytial Virus (RSV) (33114415716)](https://upload.wikimedia.org/wikipedia/commons/d/d6/Human_Respiratory_Syncytial_Virus_%28RSV%29_%2833114415716%29.jpg)
RSV is a medium-sized (~150
nm)
enveloped virus
A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes.
Numerous human pathogenic viruses in circulation are encase ...
. While most particles are spherical, filamentous species have also been identified.
The genome rests within a helical nucleocapsid and is surrounded by matrix protein and an envelope containing viral glycoproteins.
There are 11 proteins, described further in the table below.
=G protein
=
![Human Respiratory Syncytial Virus (RSV) (52456711008)](https://upload.wikimedia.org/wikipedia/commons/1/10/Human_Respiratory_Syncytial_Virus_%28RSV%29_%2852456711008%29.jpg)
Surface protein G (glycoprotein) is primarily responsible for viral attachment to host cells.
This protein is highly variable between strains.
G protein exists in both membrane-bound and secreted forms.
The membrane-found form is responsible for attachment by binding to
glycosaminoglycan
Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case ...
s (GAGs), such as
heparan sulfate
Heparan sulfate (HS) is a linear polysaccharide found in all animal tissues. It occurs as a proteoglycan (HSPG, i.e. Heparan Sulfate ProteoGlycan) in which two or three HS chains are attached in close proximity to cell surface or extracellular ma ...
, on the surface of host cells.
The secreted form acts as a decoy, interacting with antigen presenting cells to inhibit antibody-mediated
neutralization.
G protein also contains a
CX3C fractalkine-like motif that binds to the CX3C chemokine receptor 1 (
CX3CR1
CX3C motif chemokine receptor 1 (CX3CR1), also known as the fractalkine receptor or G-protein coupled receptor 13 (GPR13), is a transmembrane protein of the G protein-coupled receptor 1 (GPCR1) family and the only known member of the CX3C chemokin ...
) on the surface of ciliated bronchial host cells.
This binding may alter cellular chemotaxis and reduce the migration of immune cells into the lungs of infected individuals.
G protein also alters host immune response by inhibiting signaling from several
toll-like receptor
Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system. They are single-pass membrane-spanning receptors usually expressed on sentinel cells such as macrophages and dendritic cells, that recognize ...
s, including
TLR4
Toll-like receptor 4 is a protein that in humans is encoded by the ''TLR4'' gene. TLR4 is a transmembrane protein, member of the toll-like receptor family, which belongs to the pattern recognition receptor (PRR) family. Its activation leads to an ...
.
=F protein
=
Surface protein F (fusion protein) is responsible for fusion of viral and host cell membranes, as well as syncytium formation between viral particles.
Its sequence is highly conserved between strains.
While viral attachment appears to involve both F and G proteins, F fusion occurs independently of G.
F protein exists in multiple conformational forms.
In the prefusion state (PreF), the protein exists in a trimeric form and contains the major
antigen
In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune respons ...
ic site Ø.
Ø serves as a primary target of
neutralizing antibodies
A neutralizing antibody (NAb) is an antibody that defends a cell from a pathogen or infectious particle by neutralizing any effect it has biologically. Neutralization renders the particle no longer infectious or pathogenic.
Neutralizing antibod ...
in the body.
After binding to its target on the host cell surface (its exact ligand remains unclear), PreF undergoes a
conformational change during which Ø is lost.
This change enables the protein to insert itself into the host
cell membrane
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...
and leads to fusion of the viral and host cell membranes.
A final conformational shift results in a more stable and elongated form of the protein (postfusion, PostF).
Opposite of the RSV G protein, the RSV F protein also binds to and activates toll-like receptor 4 (TLR4), initiating the innate immune response and signal transduction.
Replication cycle
Following fusion of the viral and host cell membranes, the viral
nucleocapsid (containing the viral genome) and the associated viral polymerase are delivered into the host cell
cytoplasm
In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...
. Transcription and
translation
Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transla ...
both occur within the cytoplasm. RNA-dependent RNA polymerase transcribes the genome into 10 segments of messenger RNA (
mRNA
In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein.
mRNA is created during the ...
) which is translated into structural proteins by host cell machinery. During
replication of the
negative-sense
In molecular biology and genetics, the sense of a nucleic acid molecule, particularly of a strand of DNA or RNA, refers to the nature of the roles of the strand and its complementarity (molecular biology), complement in specifying a sequence of am ...
viral genome, RNA-dependent RNA polymerase synthesizes a positive-sense complement called the antigenome. This complementary strand is used as a template to construct genomic negative-sense RNA, which is packaged into nucleocapsids and transported to the plasma membrane for assembly and particle budding.
Mechanism
Transmission
RSV is highly contagious and can cause outbreaks from both community and hospital transmission.
For each person infected with RSV, it is estimated that an average of 5 to 25 uninfected people will become infected.
RSV can spread when an infected person coughs or sneezes, releasing contaminated droplets into the air. Transmission usually occurs when these droplets come into contact with another person's eyes, nose, or mouth.
RSV can also live for up to 25 minutes on contaminated skin (i.e. hands) and several hours on other surfaces like countertops and doorknobs.
It has an
incubation period
Incubation period (also known as the latent period or latency period) is the time elapsed between exposure to a pathogenic organism, a chemical, or radiation, and when symptoms and signs are first apparent. In a typical infectious disease, the in ...
of 2 to 8 days.
Once infected, people are usually contagious for 3 to 8 days. In infants and in people with weakened immune systems, however, the virus may continue to spread for up to 4 weeks (even after they are no longer showing symptoms).
Pathogenesis
Following transmission through the nose or eyes, RSV infects
ciliated
The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike project ...
columnar epithelial cells of the upper and lower airway.
RSV continues to
replicate within these bronchial cells for about 8 days.
After the first several days, RSV-infected cells will become more rounded and ultimately slough into the smaller
bronchiole
The bronchioles or bronchioli (pronounced ''bron-kee-oh-lee'') are the smaller branches of the bronchial airways in the lower respiratory tract. They include the terminal bronchioles, and finally the respiratory bronchioles that mark the start ...
s of the lower airway.
This sloughing mechanism is also thought to be responsible for the spread of virus from the upper to lower respiratory tract.
Infection causes generalized inflammation within the lungs, including the migration and infiltration of inflammatory cells (such as monocytes and T-cells), necrosis of the epithelial cell wall,
edema, and increased mucous production.
Inflammation and cell damage tends to be patchy rather than diffuse.
Together, the sloughed epithelial cells, mucous plugs, and accumulated immune cells cause obstruction of the lower airway.
Diagnosis
Laboratory diagnosis
A variety of laboratory tests are available for the diagnosis of RSV infection. While the American Academy of Pediatrics (AAP) does not routinely recommend the use of lab testing to diagnosis RSV bronchiolitis (for which the treatment is largely supportive),
confirmation of RSV infection may be warranted in high-risk groups if the result will guide clinical decisions. Common identification techniques include antigen testing, molecular testing, and viral culture.
Antigen testing
Antigen testing involves detection of RSV antigen fragments (or pieces of molecular viral structures), usually from an
nasopharyngeal
The pharynx (plural: pharynges) is the part of the throat behind the mouth and nasal cavity, and above the oesophagus and trachea (the tubes going down to the stomach and the lungs). It is found in vertebrates and invertebrates, though its struct ...
swab or aspirate. This can be accomplished either by viewing fluorescently labeled antigens under a microscope (direct fluorescence assay, or DFA) or using a commercially available
rapid antigen detection test
A rapid antigen test (RAT), sometimes called a rapid antigen detection test (RADT), antigen rapid test (ART), or loosely just a rapid test, is a rapid diagnostic test suitable for point-of-care testing that directly detects the presence or absenc ...
(RADT).
Overall, antigen testing is highly
sensitive in young children (80–90%) but substantially less reliable in older children and adults, who have less viral shedding.
Antigen tests are also subject to higher false positive rates outside of the peak RSV season, such as in the summer months. In these scenarios, the use of either viral culture or nucleic acid amplification testing (NAAT) may aid in an accurate RSV diagnosis.
*
Rapid antigen detection test
A rapid antigen test (RAT), sometimes called a rapid antigen detection test (RADT), antigen rapid test (ART), or loosely just a rapid test, is a rapid diagnostic test suitable for point-of-care testing that directly detects the presence or absenc ...
s (RADT) are commonly used as
point-of-care testing
Point-of-care testing (POCT or bedside testing) is defined as medical diagnostic testing at or near the point of care—that is, at the time and place of patient care. This contrasts with the historical pattern in which testing was wholly or most ...
due to their ease of use and quick turnaround time (as little as 10 minutes). These include both
enzyme immunosorbent assays (EIA) and
chromatographic
In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system (a ...
immunoassays (CIA).
*
Direct fluorescence assay (DFA) allows for direct microscopic examination of virus-infected cells. The sensitivity of DFA testing depends on an adequate specimen.
Molecular testing
Molecular assays, such as
nucleic acid amplification tests
A nucleic acid test (NAT) is a technique used to detect a particular nucleic acid sequence and thus usually to detect and identify a particular species or subspecies of organism, often a virus or bacterium that acts as a pathogen in blood, tiss ...
(NAATs), enable sensitive detection of very small amounts of virus in nasopharyngeal swabs and aspirates. NAAT assays such as polymerase chain reaction (PCR) detect virus-specific genetic material, rather than viral antigens. They have a
sensitivity and specificity
''Sensitivity'' and ''specificity'' mathematically describe the accuracy of a test which reports the presence or absence of a condition. Individuals for which the condition is satisfied are considered "positive" and those for which it is not are ...
approaching 100%.
However, they tend to be more expensive and require more complex equipment than other testing methods, making them less practical in resource limited areas.
*
Polymerase chain reaction
The polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies (complete or partial) of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it (or a part of it) ...
(PCR) is type of NAAT which allows a very small sample of genetic material to be rapidly amplified into millions of copies for study. PCR is more sensitive than either antigen testing or viral culture.
Therefore, it can be used to detect virus in those with lower viral shedding, such as older children and adults. It may also be used to detect the disease earlier in at-risk individuals (such as hospitalized or immunocompromised patients), when the viral burden may still be too low to be identified by traditional techniques. Because of its sensitivity, PCR can also often detect asymptomatic carriers and may remain positive even days after an infection has clinically resolved.
* Multi-pathogen panels are also available, which can detect the presence of multiple viral infections (including RSV) in a single patient.
Viral culture
In traditional
viral culture
Viral culture is a laboratory technique in which samples of a virus are placed to different cell lines which the virus being tested for its ability to infect. If the cells show changes, known as cytopathic effects, then the culture is positive.
...
, a sample of the virus is introduced to different
cell lines
An immortalised cell line is a population of cells from a multicellular organism which would normally not proliferate indefinitely but, due to mutation, have evaded normal cellular senescence and instead can keep undergoing division. The cells ...
and allowed to replicate so it can be studied. Benefits of this technique include the ability to perform genetic characterization, strain typing, and antiviral susceptibility testing. However, it is limited by its prolonged turnaround time of 3–7 days, making it less common in patient care and more common in research settings.
Serologic testing
Serology
Serology is the scientific study of serum and other body fluids. In practice, the term usually refers to the diagnostic identification of antibodies in the serum. Such antibodies are typically formed in response to an infection (against a given mic ...
(the measurement of virus-specific
antibodies in the
serum) is not frequently used in RSV diagnosis. The time required for the body to mount a significant serologic response (and demonstrate a significant rise in antibodies that can be detected in serum) is usually not useful in guiding patient care.
Up to 30% of patients with documented RSV infection will have negative serology results.
As such, this method is generally reserved for research and surveillance studies.
Imaging findings
![RSV](https://upload.wikimedia.org/wikipedia/commons/7/77/RSV.PNG)
Chest X-rays findings in children with RSV bronchiolitis are generally nonspecific and include
perihilar markings, patchy hyperinflation, and
atelectasis
Atelectasis is the collapse or closure of a lung resulting in reduced or absent gas exchange. It is usually unilateral, affecting part or all of one lung. It is a condition where the alveoli are deflated down to little or no volume, as distinct ...
.
However, the
American Academy of Pediatrics (AAP) does not recommend routine imaging for children with presumed RSV bronchiolitis because it does not change clinical outcomes and is associated with increased antibiotic use.
Chest X-ray is sometimes considered when the diagnosis of bronchiolitis is unclear or when there is an unexpected worsening.
In adults with RSV infection, chest films are often normal or demonstrate nonspecific changes consistent with viral pneumonia, such as patchy bilateral infiltrates.
Differential diagnosis
The differential diagnosis for individuals presenting with signs and symptoms of upper and lower respiratory tract infection includes other viral infections (such as
rhinovirus
The rhinovirus (from the grc, ῥίς, rhis "nose", , romanized: "of the nose", and the la, vīrus) is the most common viral infectious agent in humans and is the predominant cause of the common cold. Rhinovirus infection proliferates in tem ...
,
metapneumovirus
''Metapneumovirus'' is a genus of viruses in the family ''Pneumoviridae''.
The genus contains two species:
* Avian metapneumovirus (aMPV)
* Human metapneumovirus
''Human metapneumovirus'' (HMPV) is a negative-sense single-stranded RNA virus ...
, and influenza) and primary bacterial pneumonia. In children,
inhaled foreign bodies and congenital conditions such as
cystic fibrosis or asthma should also be considered.
Prevention
General prevention measures
The main prevention measure is to avoid close contact with infected individuals. In community and daycare settings, careful
hand washing
Hand washing (or handwashing), also known as hand hygiene, is the act of cleaning one's hands with soap or handwash and water to remove viruses/bacteria/microorganisms, dirt, grease, or other harmful and unwanted substances stuck to the hands ...
can help reduce transmission. In hospital settings, strict adherence to infection control measures can help prevent the spread of RSV to high-risk individuals. Alcohol-based disinfectants are recommended for hand decontamination.
Immunoprophylaxis
Although there is no vaccine against RSV,
passive immunization Passive immunity is the transfer of active humoral immunity of ready-made antibodies. Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta, and it can also be induced artificially, when ...
is available to prevent RSV infection and hospitalization in the highest risk infants. Historically, RSV-specific
intravenous immunoglobin (IVIG) was used to provide passive immunity. This involved monthly administration of RSV-neutralizing
antibodies (or immunoglobins) from human donors recovering from the disease. While this transfer of antibodies was reasonably effective in providing short-term immunization to at-risk infants, it was limited by both its
intravenous administration and cost.
RSV-IVIG has since been replaced with the use of a
monoclonal antibody
A monoclonal antibody (mAb, more rarely called moAb) is an antibody produced from a cell Lineage made by cloning a unique white blood cell. All subsequent antibodies derived this way trace back to a unique parent cell.
Monoclonal antibodies ...
(MAb) that can be delivered through
muscular injection. While several monoclonal antibodies have been developed for RSV prophylaxis, the most successful of these has been palivizumab (brand name Synagis).
Palivizumab
Palivizumab, sold under the brand name Synagis, is a monoclonal antibody produced by recombinant DNA
Recombinant DNA (rDNA) molecules are DNA molecules formed by laboratory methods of genetic recombination (such as molecular cloning) that br ...
is a monoclonal antibody directed against the surface fusion (F) protein of the RSV virus. It was licensed in 1998 and is effective in providing temporary prophylaxis against both RSV A and B. It is given by monthly injections, which are begun just prior to the RSV season and are usually continued for five months. Palivizumab has been shown to reduce both hospitalization rates and all-cause mortality in certain groups of high-risk children (such as those with chronic lung disease, congenital heart disease, and those born preterm).
However, its cost limits its use in many parts of the world. More potent derivatives of this antibody have since been developed (including
motavizumab) but were associated with considerable adverse events.
The American Academy of Pediatrics (AAP 2014) recommends RSV prophylaxis with palivizumab during RSV season for:
* Infants born at ≤28 weeks 6 days
gestational age
In obstetrics, gestational age is a measure of the age of a pregnancy which is taken from the beginning of the woman's last menstrual period (LMP), or the corresponding age of the gestation as estimated by a more accurate method if available. Su ...
and <12 months at the start of RSV season
* Infants <12 months old with
chronic lung disease of prematurity
* Infants ≤12 months old with hemodynamically significant
congenital heart disease
A congenital heart defect (CHD), also known as a congenital heart anomaly and congenital heart disease, is a defect in the structure of the heart or great vessels that is present at birth. A congenital heart defect is classed as a cardiovascular ...
* Infants <24 months old with chronic lung disease of prematurity requiring medical therapy
Per AAP guidelines, palivizumab prophylaxis may also be considered in infants with:
*
Congenital airway abnormality
*
Neuromuscular disorder
A neuromuscular disease is any disease affecting the peripheral nervous system (PNS), the neuromuscular junction, or skeletal muscle, all of which are components of the motor unit. Damage to any of these structures can cause muscle atrophy and weak ...
* Cystic fibrosis
* Severe immunocompromise
* Recent or upcoming
heart transplantation
A heart transplant, or a cardiac transplant, is a surgical transplant procedure performed on patients with end-stage heart failure or severe coronary artery disease when other medical or surgical treatments have failed. , the most common procedu ...
Nirsevimab (Beyfortus) was approved for medical use in the European Union in November 2022.
Vaccines
, there is no licensed
vaccine
A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified. to prevent infection by RSV. There has been tremendous interest and research in RSV vaccine discovery, given the virus's significant
disease burden
Disease burden is the impact of a health problem as measured by financial cost, mortality, morbidity, or other indicators. It is often quantified in terms of quality-adjusted life years (QALYs) or disability-adjusted life years (DALYs). Bot ...
and the relative lack of disease-specific therapies. However, vaccine development has faced significant obstacles that have blocked its progress. Among these are infant-specific factors, such as the immature infant immune system and the presence of
maternal antibodies Passive immunity is the transfer of active humoral immunity of ready-made antibodies. Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta, and it can also be induced artificially, when h ...
, which make infantile
immunization
Immunization, or immunisation, is the process by which an individual's immune system becomes fortified against an infectious agent (known as the immunogen).
When this system is exposed to molecules that are foreign to the body, called ''non-se ...
difficult.
Attempts to develop an RSV vaccine began in the 1960s with a
formalin
Formaldehyde ( , ) ( systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section F ...
-
inactivated vaccine
An inactivated vaccine (or killed vaccine) is a vaccine consisting of virus particles, bacteria, or other pathogens that have been grown in culture and then killed to destroy disease-producing capacity. In contrast, live vaccines use pathogens ...
that was developed for use in infants and children. While a similar method was used to create a safe and effective
poliovirus vaccine, this vaccine resulted in a dangerous phenomenon that came to be known as
vaccine-associated enhanced respiratory disease
Vaccine-associated enhanced respiratory disease (VAERD), or simply enhanced respiratory disease (ERD), refers to an adverse event where an exacerbated course of respiratory disease occurs with higher incidence in the vaccinated population in com ...
(VAERD). In VAERD, the vaccinated infants went on to develop significantly worse respiratory disease than non-vaccinated infants during subsequent natural infection. Some 80% of such children (vs. 5% of virus-exposed controls) were hospitalized, with two cases leading to death. This disaster led to extreme caution and hindered vaccine development for many years.
A 2019 paper claimed that research toward vaccine development had greatly advanced over the preceding 5–10 years, with more than 30 candidates in some stage of development.
The same study predicted that a vaccine would be available within 10 years. The types of vaccines currently in research fall into five broad categories:
live-attenuated,
protein subunit,
vector-based, particle-based, and
messenger RNA. Each targets different immune responses, and thus may be better suited to prevent disease in different at-risk groups. Live-attenuated vaccines have shown some success in RSV-naive infants. Other vaccine candidates hope to target vulnerable populations across the lifespan, including pregnant women and the elderly.
Treatment
Supportive care
Treatment for RSV infection is focused primarily on supportive care. This may include monitoring a patient's breathing or using suction to remove secretions from the upper airway.
Supplemental oxygen
Oxygen therapy, also known as supplemental oxygen, is the use of oxygen as medical treatment. Acute indications for therapy include hypoxemia (low blood oxygen levels), carbon monoxide toxicity and cluster headache. It may also be prophylactical ...
may also be delivered though a
nasal cannula
The nasal cannula (NC) is a device used to deliver supplemental oxygen or increased airflow to a patient or person in need of respiratory help. This device consists of a lightweight tube which on one end splits into two prongs which are place ...
or face mask in order to improve airflow. In severe cases of respiratory failure,
intubation
Intubation (sometimes entubation) is a medical procedure involving the insertion of a tube into the body. Patients are generally anesthetized beforehand. Examples include tracheal intubation, and the balloon tamponade with a Sengstaken-Blake ...
and mechanical ventilation may be required to support breathing. If signs of dehydration are present, fluids may also be given orally or through an IV.
Additional supportive treatments have been investigated specifically in infants hospitalized with RSV bronchiolitis. These include the following:
*
Nebulized hypertonic saline
Saline (also known as saline solution) is a mixture of sodium chloride (salt) and water. It has a number of uses in medicine including cleaning wounds, removal and storage of contact lenses, and help with dry eyes. By injection into a vein ...
has been shown to reduce length of hospitalization and reduce clinical severity in infants with viral bronchiolitis. A possible mechanism is reducing airway edema and mucus plugging to decrease airway obstruction.
*
Heliox
Heliox is a breathing gas mixture of helium (He) and oxygen (O2). It is used as a medical treatment for patients with difficulty breathing because mixture generates less resistance than atmospheric air when passing through the airways of the lung ...
, a mixture of oxygen with helium, may improve respiratory distress within the first hour after starting treatment. It works by reducing airway resistance and decreasing the work of breathing. However, it has not been shown to impact overall illness outcomes.
*
Chest physiotherapy has not been found to reduce disease severity and is not routinely recommended.
* Inhaled recombinant human
deoxyribonuclease Deoxyribonuclease (DNase, for short) refers to a group of glycoprotein endonucleases which are enzymes that catalyze the hydrolytic cleavage of phosphodiester linkages in the DNA backbone, thus degrading DNA. The role of the DNase enzyme in cells ...
(rhDNase), an enzyme that digests the DNA that contributes to mucus plugging and airway obstruction, has not been shown to improve clinical outcomes in this group.
Viral-specific therapies
*
Ribavirin
Ribavirin, also known as tribavirin, is an antiviral medication used to treat RSV infection, hepatitis C and some viral hemorrhagic fevers. For hepatitis C, it is used in combination with other medications such as simeprevir, sofosbuvir, pe ...
is the only
antiviral
Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Unlike most antibiotics, antiviral drugs do no ...
medication currently licensed for the treatment of RSV in children. It is a
guanosine
Guanosine (symbol G or Guo) is a purine nucleoside comprising guanine attached to a ribose ( ribofuranose) ring via a β-N9- glycosidic bond. Guanosine can be phosphorylated to become guanosine monophosphate (GMP), cyclic guanosine monophosphate ...
analog that acts by inhibiting viral
RNA synthesis
Transcription is the process of copying a segment of DNA into RNA. The segments of DNA transcribed into RNA molecules that can encode proteins are said to produce messenger RNA (mRNA). Other segments of DNA are copied into RNA molecules called ...
and capping. It was originally approved in 1986 for treatment of RSV infection. However, the use of ribavirin remains controversial due to unclear evidence regarding efficacy, concerns about toxicity to exposed staff members, as well as cost.
As such, most current guidelines do not make specific recommendations regarding its use in children. In adults, ribavirin is
used off-label and is generally reserved for the severely immunocompromised, such as those undergoing
hematopoietic stem cell transplants.
*
Presatovir
Presatovir (GS-5806) is an antiviral drug which was developed as a treatment for respiratory syncytial virus. It acts as a fusion inhibitor, and has shown promising results in Phase II clinical trials.
See also
* Palivizumab
* Lumicitabine
* Zi ...
, an experimental
antiviral
Antiviral drugs are a class of medication used for treating viral infections. Most antivirals target specific viruses, while a broad-spectrum antiviral is effective against a wide range of viruses. Unlike most antibiotics, antiviral drugs do no ...
drug, has shown promising results in
clinical trial
Clinical trials are prospective biomedical or behavioral research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, diet ...
s but has not yet been approved for medical use. It acts as a fusion inhibitor by inhibiting the RSV F protein.
* Immunoglobins, both RSV-specific and non-specific, have historically been used for RSV-related illness. However, there is currently insufficient evidence to support the use of immunoglobins in children with RSV infection.
Anti-inflammatories
* Corticosteroids (systemic or inhaled) have not been found to decrease hospitalization length or disease severity in viral bronchiolitis.
Their use may also prolong viral shedding, and thus is not commonly recommended. However, the use of oral corticosteroids remains common in adults with RSV-related exacerbation of underlying lung disease.
*
Leukotriene inhibitors such as
Montelukast
Montelukast, sold under the brand name Singulair among others, is a medication used in the maintenance treatment of asthma. It is generally less preferred for this use than inhaled corticosteroids. It is not useful for acute asthma attacks. Ot ...
have been used in the treatment of infants and children with bronchiolitis. However, the evidence supporting their use remains inconsistent with no definitive conclusions on their efficacy.
Bronchodilators
Bronchodilator
A bronchodilator or broncholytic (although the latter occasionally includes secretory inhibition as well) is a substance that dilates the bronchi and bronchioles, decreasing resistance in the respiratory airway and increasing airflow to the lung ...
s, medications commonly used to treat asthma, are sometimes used to treat the wheezing associated with RSV infection. These medications (such as
albuterol
Salbutamol, also known as albuterol and sold under the brand name Ventolin among others, is a medication that opens up the medium and large airways in the lungs. It is a short-acting β2 adrenergic receptor agonist which works by causing rel ...
or
salbutamol) are
beta-agonists that relax the muscles of the airways to allow for improved airflow. However, bronchodilators have not been found to improve clinical severity of infection or rate of hospitalization among those with RSV infection. Given their limited benefit, plus their
adverse event
An adverse event (AE) is any untoward medical occurrence in a patient or clinical investigation subject administered a pharmaceutical product and which does not necessarily have a causal relationship with this treatment. An adverse event can ther ...
profile, they are not routinely recommended for use in RSV bronchiolitis.
Antibiotics
Antibiotic therapy is not appropriate for treatment of RSV-related bronchiolitis or viral pneumonia. Antibiotics target
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
l pathogens, not
viral pathogens such as RSV. However, antibiotics may be considered if there is clear evidence that a secondary bacterial infection has developed.
Ear infections
Otitis is a general term for inflammation or infection, inner ear infection, middle ear infection of the ear, in both humans and other animals. When infection is present, it may be viral or bacterial. When inflammation is present due to fluid bui ...
may also develop in a small number of infants with RSV bronchiolitis, in which case oral antibiotics may sometimes be used.
Epidemiology
Infants and children
Worldwide, RSV is the leading cause of bronchiolitis and pneumonia in infants and children under the age of 5. The risk of serious infection is highest during the first 6 months of life. Of those infected with RSV, 2–3% will develop
bronchiolitis
Bronchiolitis is inflammation of the small airways in the lungs. Acute bronchiolitis is due to a viral infection usually affecting children younger than two years of age. Symptoms may include fever, cough, runny nose, wheezing, and breathing ...
, necessitating hospitalization.
Each year, approximately 30 million acute respiratory illnesses and over 60,000 childhood deaths are caused by RSV worldwide. An estimated 87% of infants will have experienced an RSV infection by the age of 18 months, and nearly all children will have been infected by 3 years. In the United States, RSV is responsible for up to 20% of acute respiratory infection hospitalizations in children under the age of 5. However, the vast majority of RSV-related deaths occur in low-income countries that lack access to basic supportive care.
Adults
It is rare for healthy young adults to develop severe illness requiring hospitalization from RSV. However, it is now recognized as a significant cause of morbidity and mortality in certain adult populations, including the elderly and those with underlying heart or lung diseases. Its clinical impact among elderly adults is estimated to be similar to that of influenza.
Each year, approximately 5–10% of nursing home residents will experience RSV infection, with significant rates of pneumonia and death. RSV is also responsible for 2–5% of adult
community-acquired pneumonia
Community-acquired pneumonia (CAP) refers to pneumonia (any of several lung diseases) contracted by a person outside of the healthcare system. In contrast, hospital-acquired pneumonia (HAP) is seen in patients who have recently visited a hospital ...
s.
Immunocompromised
In both adults and children, immunosuppression increases susceptibility to RSV infection. Children living with
HIV
The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immune ...
are more likely to develop acute illness, and are 3.5 times more likely to require hospitalization than children without HIV.
Bone marrow transplant
Hematopoietic stem-cell transplantation (HSCT) is the transplantation of multipotent hematopoietic stem cells, usually derived from bone marrow, peripheral blood, or umbilical cord blood in order to replicate inside of a patient and to produce ...
patients prior to marrow engraftment are at particularly high risk, with RSV accounting for nearly half of the viral infections in this population. This group has also demonstrated mortality rates of up to 80% among those with RSV pneumonia.
While infection may occur within the community, hospital-acquired infection is thought to account for 30–50% of cases among immunocompromised individuals.
Seasonality
RSV seasonality varies around the world. In
temperate climate
In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout ...
s, infection rates tend to be highest during the cold winter months. This is often attributed to increased indoor crowding and increased viral stability in the lower temperatures. In tropical and arctic climates, however, the annual variation is less well defined and seems to be more prevalent during the rainy season.
Annual epidemics are generally caused by the presence of several different viral strains. Subtype A and B viruses will often circulate simultaneously within a specific geographic region, although group A viruses are more prevalent.
COVID-19
Public health measures taken in response to the
COVID-19 pandemic
The COVID-19 pandemic, also known as the coronavirus pandemic, is an ongoing global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identi ...
resulted in a significant decline in the prevalence of RSV. There was then a
significant unseasonal rebound when lockdowns and other restrictive measures were relaxed. In November 2022, the RSV hospitalization rate for newborns was seven times the rate in 2018. This, combined with increasing influenza circulation caused Oregon to declare a state of emergency. The
Children's Hospital Association
The Children's Hospital Association (CHA), is an organization of children's hospitals with more than 200 members in the United States, Australia, Canada, Italy, Mexico and Puerto Rico.
CHA has offices located in Lenexa, Kansas
Lenexa is a c ...
and the
American Academy of Pediatrics asked Biden to declare a state of emergency.
History
RSV was first discovered in 1956 when researchers isolated a virus from a population of
chimpanzees with respiratory illness. They named the virus CCA (''Chimpanzee Coryza Agent''). In 1957, this same virus was identified by
Robert M. Chanock in children with respiratory illness. Studies of human antibodies in infants and children revealed that the infection was common in early life. The virus was later renamed human orthopneumovirus, or human respiratory syncytial virus (hRSV).
Several other pneumoviruses exist that show great similarity to hRSV. Most notable of these is
bovine
Bovines (subfamily Bovinae) comprise a diverse group of 10 genera of medium to large-sized ungulates, including cattle, bison, African buffalo, water buffalos, and the four-horned and spiral-horned antelopes. The evolutionary relationship betwe ...
RSV (bRSV), which shares approximately 80% of its genome with hRSV. It also shares hRSV's predilection for the young, causing more severe disease in calves less than 6 months old. Because bRSV-infected calves have an almost identical presentation to hRSV-infected children, this has proven to be an important
animal model
An animal model (short for animal disease model) is a living, non-human, often genetic-engineered animal used during the research and investigation of human disease, for the purpose of better understanding the disease process without the risk of ha ...
in RSV research.
Notes
References
{{Taxonbar, from=Q1052913
Atypical pneumonias
Viral respiratory tract infections