Pneumonia is an inflammatory condition of the lung affecting primarily
the small air sacs known as alveoli. Typically symptoms include
some combination of productive or dry cough, chest pain, fever, and
trouble breathing. Severity is variable.
Pneumonia is usually caused by infection with viruses or bacteria and
less commonly by other microorganisms, certain medications and
conditions such as autoimmune diseases. Risk factors include
other lung diseases such as cystic fibrosis, COPD, and asthma,
diabetes, heart failure, a history of smoking, a poor ability to cough
such as following a stroke, or a weak immune system. Diagnosis is
often based on the symptoms and physical examination. Chest X-ray,
blood tests, and culture of the sputum may help confirm the
diagnosis. The disease may be classified by where it was acquired
with community, hospital, or health care associated pneumonia.
Vaccines to prevent certain types of pneumonia are available. Other
methods of prevention include handwashing and not smoking.
Treatment depends on the underlying cause.
Pneumonia believed to
be due to bacteria is treated with antibiotics. If the pneumonia
is severe, the affected person is generally hospitalized. Oxygen
therapy may be used if oxygen levels are low.
Pneumonia affects approximately 450 million people globally (7%
of the population) and results in about 4 million deaths per
Pneumonia was regarded by
William Osler in the 19th
century as "the captain of the men of death". With the
introduction of antibiotics and vaccines in the 20th century, survival
improved. Nevertheless, in developing countries, and among the
very old, the very young, and the chronically ill, pneumonia remains a
leading cause of death.
Pneumonia often shortens suffering
among those already close to death and has thus been called "the old
1 Signs and symptoms
4.1 Physical exam
4.5 Differential diagnosis
7.1 Clinical prediction rules
7.2 Pleural effusion, empyema, and abscess
7.3 Respiratory and circulatory failure
10 Society and culture
13 External links
Signs and symptoms
Shortness of breath
Main symptoms of infectious pneumonia
People with infectious pneumonia often have a productive cough, fever
accompanied by shaking chills, shortness of breath, sharp or stabbing
chest pain during deep breaths, and an increased rate of breathing.
In the elderly, confusion may be the most prominent sign.
The typical signs and symptoms in children under five are fever,
cough, and fast or difficult breathing.
Fever is not very
specific, as it occurs in many other common illnesses, may be absent
in those with severe disease, malnutrition or in the elderly. In
addition, a cough is frequently absent in children less than 2 months
old. More severe signs and symptoms in children may include
blue-tinged skin, unwillingness to drink, convulsions, ongoing
vomiting, extremes of temperature, or a decreased level of
Bacterial and viral cases of pneumonia usually present with similar
symptoms. Some causes are associated with classic, but
non-specific, clinical characteristics.
Pneumonia caused by Legionella
may occur with abdominal pain, diarrhea, or confusion, while
pneumonia caused by
Streptococcus pneumoniae is associated with rusty
colored sputum, and pneumonia caused by
Klebsiella may have bloody
sputum often described as "currant jelly". Bloody sputum (known as
hemoptysis) may also occur with tuberculosis, Gram-negative pneumonia,
and lung abscesses as well as more commonly with acute bronchitis.
Mycoplasma pneumonia may occur in association with swelling of the
lymph nodes in the neck, joint pain, or a middle ear infection.
Viral pneumonia presents more commonly with wheezing than does
Pneumonia was historically divided into
"typical" and "atypical" based on the belief that the presentation
predicted the underlying cause. However, evidence has not
supported this distinction, thus it is no longer emphasized.
The bacterium Streptococcus pneumoniae, a common cause of pneumonia,
imaged by an electron microscope
Pneumonia is due to infections caused primarily by bacteria or viruses
and less commonly by fungi and parasites. Although there are more than
100 strains of infectious agents identified, only a few are
responsible for the majority of the cases. Mixed infections with both
viruses and bacteria may occur in up to 45% of infections in children
and 15% of infections in adults. A causative agent may not be
isolated in approximately half of cases despite careful testing.
The term pneumonia is sometimes more broadly applied to any condition
resulting in inflammation of the lungs (caused for example by
autoimmune diseases, chemical burns or drug reactions); however, this
inflammation is more accurately referred to as pneumonitis.
Conditions and risk factors that predispose to pneumonia include
smoking, immunodeficiency, alcoholism, chronic obstructive pulmonary
disease, asthma, chronic kidney disease, liver disease, and old
age. The use of acid-suppressing medications—such as
proton-pump inhibitors or H2 blockers—is associated with an
increased risk of pneumonia. Approximately 10% of people who
require mechanical ventilation develop ventilator associated
pneumonia, and people with gastric feeding tube have an increased
risk of developing of aspiration pneumonia.
Main article: Bacterial pneumonia
Cavitating pneumonia as seen on CT.
Pneumonia due to MRSA.
Bacteria are the most common cause of community-acquired pneumonia
Streptococcus pneumoniae isolated in nearly 50% of
cases. Other commonly isolated bacteria include Haemophilus
influenzae in 20%,
Chlamydophila pneumoniae in 13%, and Mycoplasma
pneumoniae in 3% of cases; Staphylococcus aureus; Moraxella
Legionella pneumophila and Gram-negative bacilli. A
number of drug-resistant versions of the above infections are becoming
more common, including drug-resistant
Streptococcus pneumoniae (DRSP)
Staphylococcus aureus (MRSA).
The spreading of organisms is facilitated when risk factors are
Alcoholism is associated with Streptococcus pneumoniae,
anaerobic organisms, and Mycobacterium tuberculosis; smoking
facilitates the effects of Streptococcus pneumoniae, Haemophilus
influenzae, Moraxella catarrhalis, and
Exposure to birds is associated with Chlamydia psittaci; farm animals
with Coxiella burnetti; aspiration of stomach contents with anaerobic
organisms; and cystic fibrosis with
Pseudomonas aeruginosa and
Streptococcus pneumoniae is more common in
the winter, and should be suspected in persons aspirating a large
amount of anaerobic organisms.
Main article: Viral pneumonia
In adults, viruses account for approximately a third and in
children for about 15% of pneumonia cases. Commonly implicated
agents include rhinoviruses, coronaviruses, influenza virus,
respiratory syncytial virus (RSV), adenovirus, and
Herpes simplex virus
Herpes simplex virus rarely causes pneumonia,
except in groups such as: newborns, persons with cancer, transplant
recipients, and people with significant burns. People following
organ transplantation or those otherwise-immunocompromised present
high rates of cytomegalovirus pneumonia. Those with viral
infections may be secondarily infected with the bacteria Streptococcus
pneumoniae, Staphylococcus aureus, or Haemophilus influenzae,
particularly when other health problems are present. Different
viruses predominate at different periods of the year; during influenza
season, for example, influenza may account for over half of all viral
cases. Outbreaks of other viruses also occasionally occur,
including hantaviruses and coronavirus.
Main article: Fungal pneumonia
Fungal pneumonia is uncommon, but occurs more commonly in individuals
with weakened immune systems due to AIDS, immunosuppressive drugs, or
other medical problems. It is most often caused by Histoplasma
capsulatum, blastomyces, Cryptococcus neoformans, Pneumocystis
jiroveci (pneumocystis pneumonia, or PCP), and Coccidioides immitis.
Histoplasmosis is most common in the Mississippi River basin, and
coccidioidomycosis is most common in the Southwestern United
States. The number of cases has been increasing in the later half
of the 20th century due to increasing travel and rates of
immunosuppression in the population. For people infected with
HIV/AIDS, PCP is a common opportunistic infection.
Main article: Parasitic pneumonia
A variety of parasites can affect the lungs, including Toxoplasma
gondii, Strongyloides stercoralis, Ascaris lumbricoides, and
Plasmodium malariae. These organisms typically enter the body
through direct contact with the skin, ingestion, or via an insect
vector. Except for Paragonimus westermani, most parasites do not
affect specifically the lungs but involve the lungs secondarily to
other sites. Some parasites, in particular those belonging to the
Ascaris and Strongyloides genera, stimulate a strong eosinophilic
reaction, which may result in eosinophilic pneumonia. In other
infections, such as malaria, lung involvement is due primarily to
cytokine-induced systemic inflammation. In the developed world
these infections are most common in people returning from travel or in
immigrants. Around the world, these infections are most common in
Main article: Idiopathic interstitial pneumonia
Idiopathic interstitial pneumonia
Idiopathic interstitial pneumonia or noninfectious pneumonia is a
class of diffuse lung diseases. They include diffuse alveolar damage,
organizing pneumonia, nonspecific interstitial pneumonia, lymphocytic
interstitial pneumonia, desquamative interstitial pneumonia,
respiratory bronchiolitis interstitial lung disease, and usual
Pneumonia fills the lung's alveoli with fluid, hindering oxygenation.
The alveolus on the left is normal, whereas the one on the right is
full of fluid from pneumonia.
Pneumonia frequently starts as an upper respiratory tract infection
that moves into the lower respiratory tract. It is a type of
pneumonitis (lung inflammation).
Viruses may reach the lung by a number of different routes.
Respiratory syncytial virus
Respiratory syncytial virus is typically contracted when people touch
contaminated objects and then they touch their eyes or nose. Other
viral infections occur when contaminated airborne droplets are inhaled
through the mouth or nose. Once in the upper airway, the viruses
may make their way in the lungs, where they invade the cells lining
the airways, alveoli, or lung parenchyma. Some viruses such as
measles and herpes simplex may reach the lungs via the blood. The
invasion of the lungs may lead to varying degrees of cell death.
When the immune system responds to the infection, even more lung
damage may occur. Primarily white blood cells, mainly mononuclear
cells, generate the inflammation. As well as damaging the lungs,
many viruses simultaneously affect other organs and thus disrupt other
body functions. Viruses also make the body more susceptible to
bacterial infections; in this way, bacterial pneumonia can occur at
the same time as viral pneumonia.
Most bacteria enter the lungs via small aspirations of organisms
residing in the throat or nose. Half of normal people have these
small aspirations during sleep. While the throat always contains
bacteria, potentially infectious ones reside there only at certain
times and under certain conditions. A minority of types of
bacteria such as
Mycobacterium tuberculosis and
reach the lungs via contaminated airborne droplets.
spread also via the blood. Once in the lungs, bacteria may invade
the spaces between cells and between alveoli, where the macrophages
and neutrophils (defensive white blood cells) attempt to inactivate
the bacteria. The neutrophils also release cytokines, causing a
general activation of the immune system. This leads to the fever,
chills, and fatigue common in bacterial pneumonia. The
neutrophils, bacteria, and fluid from surrounding blood vessels fill
the alveoli, resulting in the consolidation seen on chest X-ray.
Crackles heard in the lungs of a person with pneumonia using a
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Pneumonia is typically diagnosed based on a combination of physical
signs and a chest X-ray. However, the underlying cause can be
difficult to confirm, as there is no definitive test able to
distinguish between bacterial and non-bacterial origin.
The World Health Organization
The World Health Organization has defined pneumonia in children
clinically based on either a cough or difficulty breathing and a rapid
respiratory rate, chest indrawing, or a decreased level of
consciousness. A rapid respiratory rate is defined as greater than
60 breaths per minute in children under 2 months old, greater than 50
breaths per minute in children 2 months to 1 year old, or greater than
40 breaths per minute in children 1 to 5 years old. In children,
low oxygen levels and lower chest indrawing are more sensitive than
hearing chest crackles with a stethoscope or increased respiratory
rate. Grunting and nasal flaring may be other useful signs in
children less than five years old.
In general, in adults, investigations are not needed in mild
cases. There is a very low risk of pneumonia if all vital signs
and auscultation are normal. In persons requiring hospitalization,
pulse oximetry, chest radiography and blood tests—including a
complete blood count, serum electrolytes,
C-reactive protein level,
and possibly liver function tests—are recommended. Procalcitonin
may help determine the cause and support who should receive
The diagnosis of influenza-like illness can be made based on the signs
and symptoms; however, confirmation of an influenza infection requires
testing. Thus, treatment is frequently based on the presence of
influenza in the community or a rapid influenza test.
Physical examination may sometimes reveal low blood pressure, high
heart rate, or low oxygen saturation. The respiratory rate may be
faster than normal, and this may occur a day or two before other
signs. Examination of the chest may be normal, but it may show
decreased chest expansion on the affected side. Harsh breath sounds
from the larger airways that are transmitted through the inflamed lung
are termed bronchial breathing and are heard on auscultation with a
Crackles (rales) may be heard over the affected area
during inspiration. Percussion may be dulled over the affected
lung, and increased, rather than decreased, vocal resonance
distinguishes pneumonia from a pleural effusion.
A chest X-ray showing a very prominent wedge-shape area of airspace
consolidation in the right lung characteristic of acute bacterial
CT of the chest demonstrating right-side pneumonia (left side of the
A chest radiograph is frequently used in diagnosis. In people with
mild disease, imaging is needed only in those with potential
complications, those not having improved with treatment, or those in
which the cause is uncertain. If a person is sufficiently sick
to require hospitalization, a chest radiograph is recommended.
Findings do not always match the severity of disease and do not
reliably separate between bacterial infection and viral infection.
X-ray presentations of pneumonia may be classified as lobar pneumonia,
bronchopneumonia (also known as lobular pneumonia), and interstitial
pneumonia. Bacterial, community-acquired pneumonia classically
show lung consolidation of one lung segmental lobe, which is known as
lobar pneumonia. However, findings may vary, and other patterns
are common in other types of pneumonia.
Aspiration pneumonia may
present with bilateral opacities primarily in the bases of the lungs
and on the right side. Radiographs of viral pneumonia may appear
normal, appear hyper-inflated, have bilateral patchy areas, or present
similar to bacterial pneumonia with lobar consolidation.
Radiologic findings may not be present in the early stages of the
disease, especially in the presence of dehydration, or may be
difficult to be interpreted in the obese or those with a history of
lung disease. A
CT scan can give additional information in
Lung ultrasound may also be useful in helping
to make the diagnosis.
Pneumonia seen by ultrasound
Pneumonia seen by ultrasound
Pneumonia seen by ultrasound
Right middle lobe pneumonia in a child as seen on plain X ray
In patients managed in the community, determining the causative agent
is not cost-effective and typically does not alter management. For
people who do not respond to treatment, sputum culture should be
considered, and culture for
Mycobacterium tuberculosis should be
carried out in persons with a chronic productive cough. Testing
for other specific organisms may be recommended during outbreaks, for
public health reasons. In those hospitalized for severe disease,
both sputum and blood cultures are recommended, as well as testing
the urine for antigens to
Legionella and Streptococcus. Viral
infections can be confirmed via detection of either the virus or its
antigens with culture or polymerase chain reaction (PCR), among other
techniques. The causative agent is determined in only 15% of cases
with routine microbiological tests.
Main article: Classification of pneumonia
Pneumonitis refers to lung inflammation; pneumonia refers to
pneumonitis, usually due to infection but sometimes non-infectious,
that has the additional feature of pulmonary consolidation.
Pneumonia is most commonly classified by where or how it was acquired:
community-acquired, aspiration, healthcare-associated,
hospital-acquired, and ventilator-associated pneumonia. It may
also be classified by the area of lung affected: lobar pneumonia,
bronchial pneumonia and acute interstitial pneumonia; or by the
Pneumonia in children may additionally be
classified based on signs and symptoms as non-severe, severe, or very
The setting in which pneumonia develops is important to
treatment, as it correlates to which pathogens are likely
suspects, which mechanisms are likely, which antibiotics are
likely to work or fail, and which complications can be expected
based on the person's health status.
Main article: Community-acquired pneumonia
Community-acquired pneumonia (CAP) is acquired in the
community, outside of health care facilities. Compared with
health care–associated pneumonia, it is less likely to involve
multidrug-resistant bacteria. Although the latter are no longer rare
in CAP, they are still less likely.
Health care–associated pneumonia (HCAP) is an infection associated
with recent exposure to the health care system, including
hospital, outpatient clinic, nursing home, dialysis center,
chemotherapy treatment, or home care. HCAP is sometimes called
MCAP (medical care–associated pneumonia).
Hospital-acquired pneumonia is acquired in a hospital, specifically,
pneumonia that occurs 48 hours or more after admission, which was not
incubating at the time of admission. It is likely to involve
hospital-acquired infections, with higher risk of multidrug-resistant
pathogens. Also, because hospital patients are often ill (which is why
they are present in the hospital), accompanying disorders are an
Ventilator-associated pneumonia occurs in people breathing with the
help of mechanical ventilation. Ventilator-associated
pneumonia is specifically defined as pneumonia that arises more than
48 to 72 hours after endotracheal intubation.
Several diseases can present with similar signs and symptoms to
pneumonia, such as: chronic obstructive pulmonary disease (COPD),
asthma, pulmonary edema, bronchiectasis, lung cancer, and pulmonary
emboli. Unlike pneumonia, asthma and
COPD typically present with
wheezing, pulmonary edema presents with an abnormal electrocardiogram,
cancer and bronchiectasis present with a cough of longer duration, and
pulmonary emboli presents with acute onset sharp chest pain and
shortness of breath.
Prevention includes vaccination, environmental measures and
appropriate treatment of other health problems. It is believed
that, if appropriate preventive measures were instituted globally,
mortality among children could be reduced by 400,000; and, if proper
treatment were universally available, childhood deaths could be
decreased by another 600,000.
Vaccination prevents against certain bacterial and viral pneumonias
both in children and adults.
Influenza vaccines are modestly effective
at preventing symptoms of influenza, The Center for Disease
Control and Prevention (CDC) recommends yearly influenza vaccination
for every person 6 months and older. Immunizing health care
workers decreases the risk of viral pneumonia among their
Haemophilus influenzae and Streptococcus
pneumoniae have good evidence to support their use. There is
strong evidence for vaccinating children under the age of 2 against
Streptococcus pneumoniae (pneumococcal conjugate vaccine).
Vaccinating children against
Streptococcus pneumoniae has led to a
decreased rate of these infections in adults, because many adults
acquire infections from children. A
Streptococcus pneumoniae vaccine
is available for adults, and has been found to decrease the risk of
invasive pneumococcal disease, but there is insufficient evidence to
suggest using the pneumococcal vaccine to prevent pneumonia or
mortality in the general adult population. The CDC recommends that
young children and adults over the age of 65 receive the pneumococcal
vaccine, as well as older children or younger adults who have an
increased risk of getting pneumococcal disease. The pneumococcal
vaccine has been shown to reduce the risk of community acquired
pneumonia in people with chronic obstructive pulmonary disease (COPD),
but does not reduce mortality or the risk of hospitalization for
people with this condition. People with
COPD are suggested to have
a pneumococcal vaccination. Other vaccines for which there is
support for a protective effect against pneumonia include pertussis,
varicella, and measles.
When influenza outbreaks occur, medications such as amantadine or
rimantadine may help prevent the condition; however are associated
with side effects.
Zanamivir or oseltamivir decrease the chance
that those exposed will develop symptoms; however, it is recommended
that potential side effects are taken into account.
Smoking cessation and reducing indoor air pollution, such as that
from cooking indoors with wood or dung, are both recommended.
Smoking appears to be the single biggest risk factor for pneumococcal
pneumonia in otherwise-healthy adults. Hand hygiene and coughing
into one's sleeve may also be effective preventative measures.
Wearing surgical masks by the sick may also prevent illness.
Appropriately treating underlying illnesses (such as HIV/AIDS,
diabetes mellitus, and malnutrition) can decrease the risk of
pneumonia. In children less than 6 months of age,
exclusive breast feeding reduces both the risk and severity of
disease. In those with HIV/
AIDS and a CD4 count of less than 200
cells/uL the antibiotic trimethoprim/sulfamethoxazole decreases the
risk of Pneumocystis pneumonia and is also useful for prevention
in those that are immunocomprised but do not have HIV.
Testing pregnant women for
Group B Streptococcus
Group B Streptococcus and Chlamydia
trachomatis, and administering antibiotic treatment, if needed,
reduces rates of pneumonia in infants; preventive measures for
HIV transmission from mother to child may also be efficient.
Suctioning the mouth and throat of infants with meconium-stained
amniotic fluid has not been found to reduce the rate of aspiration
pneumonia and may cause potential harm, thus this practice is not
recommended in the majority of situations. In the frail elderly
good oral health care may lower the risk of aspiration pneumonia.
Zinc supplementation in children 2 months to five years old appears to
reduce rates of pneumonia.
For people with low levels of vitamin C in their diet or blood, taking
vitamin C supplements may be suggested to decrease the risk of
pneumonia, although there is no strong evidence of benefit. There
is insufficient evidence to recommend that the general population take
vitamin C to prevent pneumonia.
Oral antibiotics, rest, simple analgesics, and fluids usually suffice
for complete resolution. However, those with other medical
conditions, the elderly, or those with significant trouble breathing
may require more advanced care. If the symptoms worsen, the pneumonia
does not improve with home treatment, or complications occur,
hospitalization may be required. Worldwide, approximately 7–13%
of cases in children result in hospitalization, whereas in the
developed world between 22 and 42% of adults with community-acquired
pneumonia are admitted. The
CURB-65 score is useful for
determining the need for admission in adults. If the score is 0 or
1, people can typically be managed at home; if it is 2, a short
hospital stay or close follow-up is needed; if it is 3–5,
hospitalization is recommended. In children those with respiratory
distress or oxygen saturations of less than 90% should be
hospitalized. The utility of chest physiotherapy in pneumonia has
not yet been determined. Non-invasive ventilation may be
beneficial in those admitted to the intensive care unit.
Over-the-counter cough medicine has not been found to be effective
nor has the use of zinc in children. There is insufficient
evidence for mucolytics. There is no strong evidence to recommend
that children who have non-measles related pneumonia take Vitamin A
Antibiotics improve outcomes in those with bacterial pneumonia.
Increased use of antibiotics, however, may lead to the development of
antimicrobial resistant strains of bacteria.
depends initially on the characteristics of the person affected, such
as age, underlying health, and the location the infection was
Antibiotic use is also associated with side effects such as
nausea, diarrhea, dizziness, taste distortion, or headaches. In
the UK, treatment before culture results with amoxicillin is
recommended as the first line for community-acquired pneumonia, with
doxycycline or clarithromycin as alternatives. In North America,
where the "atypical" forms of community-acquired pneumonia are more
common, macrolides (such as azithromycin or erythromycin), and
doxycycline have displaced amoxicillin as first-line outpatient
treatment in adults. In children with mild or moderate
symptoms, amoxicillin taken by mouth remains the first
line. The use of fluoroquinolones in uncomplicated cases
is discouraged due to concerns about side-effects and generating
resistance in light of there being no greater clinical
For those who require hospitalization and caught their pneumonia in
the community the use of a β-lactam such as cephazolin plus macrolide
such as azithromycin or a fluoroquinolones is recommended.
The duration of treatment has traditionally been seven to ten days,
but increasing evidence suggests that shorter courses (3–5 days) may
be effective for certain types of pneumonia and may reduce the risk of
antibiotic resistance. For pneumonia that is associated
with a ventilator caused by non-fermenting Gram-negative bacilli
(NF-GNB), a shorter course of antibiotics increases the risk of that
pneumonia will return. Recommendations for hospital-acquired
pneumonia include third- and fourth-generation cephalosporins,
carbapenems, fluoroquinolones, aminoglycosides, and vancomycin.
These antibiotics are often given intravenously and used in
combination. In those treated in hospital, more than 90% improve
with the initial antibiotics. For people with ventilator-acquired
pneumonia, the choice of antibiotic therapy will depend on the
person's risk of being infected with a strain of bacteria that is
The addition of corticosteroids to standard antibiotic treatment
appears to improve outcomes, reducing the rate of mortality
and morbidity for adults with severe community acquired pneumonia, and
reducing morbidity for adults and children with non-severe community
acquired pneumonia. There are adverse effects associated with the
use of corticosteroids such as high blood sugar. There is some
evidence that adding corticosteroids to the standard PCP pneumonia
treatment may be beneficial for people who are infected with HIV.
The use of granulocyte colony stimulating factor (G-CSF) along with
antibiotics does not appear to reduce mortality and routine use for
treating pneumonia is not supported by evidence.
Neuraminidase inhibitors may be used to treat viral pneumonia caused
by influenza viruses (influenza A and influenza B). No specific
antiviral medications are recommended for other types of community
acquired viral pneumonias including
SARS coronavirus, adenovirus,
hantavirus, and parainfluenza virus.
Influenza A may be treated
with rimantadine or amantadine, while influenza A or B may be treated
with oseltamivir, zanamivir or peramivir. These are of most
benefit if they are started within 48 hours of the onset of
symptoms. Many strains of
H5N1 influenza A, also known as avian
influenza or "bird flu", have shown resistance to rimantadine and
amantadine. The use of antibiotics in viral pneumonia is
recommended by some experts, as it is impossible to rule out a
complicating bacterial infection. The British Thoracic Society
recommends that antibiotics be withheld in those with mild
disease. The use of corticosteroids is controversial.
In general, aspiration pneumonitis is treated conservatively with
antibiotics indicated only for aspiration pneumonia. The choice
of antibiotic will depend on several factors, including the suspected
causative organism and whether pneumonia was acquired in the community
or developed in a hospital setting. Common options include
clindamycin, a combination of a beta-lactam antibiotic and
metronidazole, or an aminoglycoside. Corticosteroids are
sometimes used in aspiration pneumonia, but there is limited evidence
to support their effectiveness.
With treatment, most types of bacterial pneumonia will stabilize in
3–6 days. It often takes a few weeks before most symptoms
resolve. X-ray finding typically clear within four weeks and
mortality is low (less than 1%). In the elderly or people
with other lung problems, recovery may take more than 12 weeks.
In persons requiring hospitalization, mortality may be as high as 10%,
and in those requiring intensive care it may reach 30–50%.
Pneumonia is the most common hospital-acquired infection that causes
death. Before the advent of antibiotics, mortality was typically
30% in those that were hospitalized.
Complications may occur in particular in the elderly and those with
underlying health problems. This may include, among others:
empyema, lung abscess, bronchiolitis obliterans, acute respiratory
distress syndrome, sepsis, and worsening of underlying health
Clinical prediction rules
Clinical prediction rules have been developed to more objectively
predict outcomes of pneumonia. These rules are often used in
deciding whether or not to hospitalize the person.
Pneumonia severity index (or PSI Score)
CURB-65 score, which takes into account the severity of symptoms, any
underlying diseases, and age
Pleural effusion, empyema, and abscess
A pleural effusion: as seen on chest X-ray. The A arrow indicates
fluid layering in the right chest. The B arrow indicates the width of
the right lung. The volume of the lung is reduced because of the
collection of fluid around the lung.
In pneumonia, a collection of fluid may form in the space that
surrounds the lung. Occasionally, microorganisms will infect this
fluid, causing an empyema. To distinguish an empyema from the
more common simple parapneumonic effusion, the fluid may be collected
with a needle (thoracentesis), and examined. If this shows
evidence of empyema, complete drainage of the fluid is necessary,
often requiring a drainage catheter. In severe cases of empyema,
surgery may be needed. If the infected fluid is not drained, the
infection may persist, because antibiotics do not penetrate well into
the pleural cavity. If the fluid is sterile, it must be drained only
if it is causing symptoms or remains unresolved.
In rare circumstances, bacteria in the lung will form a pocket of
infected fluid called a lung abscess.
Lung abscesses can usually
be seen with a chest X-ray but frequently require a chest
CT scan to
confirm the diagnosis. Abscesses typically occur in aspiration
pneumonia, and often contain several types of bacteria. Long-term
antibiotics are usually adequate to treat a lung abscess, but
sometimes the abscess must be drained by a surgeon or
Respiratory and circulatory failure
Pneumonia can cause respiratory failure by triggering acute
respiratory distress syndrome (ARDS), which results from a combination
of infection and inflammatory response. The lungs quickly fill with
fluid and become stiff. This stiffness, combined with severe
difficulties extracting oxygen due to the alveolar fluid, may require
long periods of mechanical ventilation for survival.
Sepsis is a potential complication of pneumonia but occurs usually in
people with poor immunity or hyposplenism. The organisms most commonly
involved are Streptococcus pneumoniae, Haemophilus influenzae, and
Klebsiella pneumoniae. Other causes of the symptoms should be
considered such as a myocardial infarction or a pulmonary
Main article: Epidemiology of pneumonia
Deaths from lower respiratory infections per million persons in 2012
Disability-adjusted life year
Disability-adjusted life year for lower respiratory infections per
100,000 inhabitants in 2004
less than 100
more than 7,000
Pneumonia is a common illness affecting approximately 450 million
people a year and occurring in all parts of the world. It is a
major cause of death among all age groups resulting in 4 million
deaths (7% of the world's total death) yearly. Rates are
greatest in children less than five, and adults older than
75 years. It occurs about five times more frequently in the
developing world than in the developed world. Viral pneumonia
accounts for about 200 million cases. In the United States,
as of 2009, pneumonia is the 8th leading cause of death.
In 2008, pneumonia occurred in approximately 156 million children
(151 million in the developing world and 5 million in the
developed world). In 2010, it resulted in 1.3 million deaths,
or 18% of all deaths in those under five years, of which 95% occurred
in the developing world. Countries with the greatest
burden of disease include India (43 million), China
(21 million) and Pakistan (10 million). It is the
leading cause of death among children in low income countries.
Many of these deaths occur in the newborn period. The World Health
Organization estimates that one in three newborn infant deaths is due
to pneumonia. Approximately half of these deaths can be
prevented, as they are caused by the bacteria for which an effective
vaccine is available. In 2011, pneumonia was the most common
reason for admission to the hospital after an emergency department
visit in the U.S. for infants and children.
WPA poster, 1936/1937
Pneumonia has been a common disease throughout human history. The
word is from Greek πνεύμων (pneúmōn) meaning "lung". The
symptoms were described by
Hippocrates (c. 460 BC – 370 BC):
"Peripneumonia, and pleuritic affections, are to be thus observed: If
the fever be acute, and if there be pains on either side, or in both,
and if expiration be if cough be present, and the sputa expectorated
be of a blond or livid color, or likewise thin, frothy, and florid, or
having any other character different from the common... When pneumonia
is at its height, the case is beyond remedy if he is not purged, and
it is bad if he has dyspnoea, and urine that is thin and acrid, and if
sweats come out about the neck and head, for such sweats are bad, as
proceeding from the suffocation, rales, and the violence of the
disease which is obtaining the upper hand." However, Hippocrates
referred to pneumonia as a disease "named by the ancients". He also
reported the results of surgical drainage of empyemas. Maimonides
(1135–1204 AD) observed: "The basic symptoms that occur in pneumonia
and that are never lacking are as follows: acute fever, sticking
pleuritic pain in the side, short rapid breaths, serrated pulse and
cough." This clinical description is quite similar to those found
in modern textbooks, and it reflected the extent of medical knowledge
Middle Ages into the 19th century.
Edwin Klebs was the first to observe bacteria in the airways of
persons having died of pneumonia in 1875. Initial work
identifying the two common bacterial causes, Streptococcus pneumoniae
Klebsiella pneumoniae, was performed by Carl Friedländer and
Albert Fraenkel in 1882 and 1884, respectively. Friedländer's
initial work introduced the Gram stain, a fundamental laboratory test
still used today to identify and categorize bacteria. Christian Gram's
paper describing the procedure in 1884 helped to differentiate the two
bacteria, and showed that pneumonia could be caused by more than one
Sir William Osler, known as "the father of modern medicine",
appreciated the death and disability caused by pneumonia, describing
it as the "captain of the men of death" in 1918, as it had overtaken
tuberculosis as one of the leading causes of death in this time. This
phrase was originally coined by
John Bunyan in reference to
"consumption" (tuberculosis). Osler also described pneumonia
as "the old man's friend" as death was often quick and painless when
there were much slower and more painful ways to die.
Several developments in the 1900s improved the outcome for those with
pneumonia. With the advent of penicillin and other antibiotics, modern
surgical techniques, and intensive care in the 20th century, mortality
from pneumonia, which had approached 30%, dropped precipitously in the
Vaccination of infants against Haemophilus influenzae
type B began in 1988 and led to a dramatic decline in cases shortly
Streptococcus pneumoniae in
adults began in 1977, and in children in 2000, resulting in a similar
Society and culture
See also: List of notable pneumonia cases
Due to the relatively low awareness of the disease, 12 November was
declared as the annual World
Pneumonia Day, a day for concerned
citizens and policy makers to take action against the disease, in
The global economic cost of community-acquired pneumonia has been
estimated at $17 billion annually. Other estimates are
considerably higher. In 2012 the estimated aggregate costs of treating
pneumonia in the United States were $20 billion; the median cost
of a single pneumonia-related hospitalization is over $15,000.
According to data released by the Centers for Medicare and Medicaid
Services, average 2012 hospital charges for inpatient treatment of
uncomplicated pneumonia in the U.S. were $24,549 and ranged as high as
$124,000. The average cost of an emergency room consult for pneumonia
was $943 and the average cost for medication was $66. Aggregate
annual costs of treating pneumonia in Europe have been estimated at
As of 2016 there has been one large trial studying the use of vitamin
D to prevent pneumonia in children, which found no effect.
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V · T · D
ICD-10: J12, J13, J14, J15, J16, J17, J18, P23
ICD-9-CM: 480-486, 770.0
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