''Legionella'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...
of pathogenic
gram-negative bacteria
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...
that includes the species ''
L. pneumophila'', causing legionellosis
(all illnesses caused by ''Legionella'') including a pneumonia-type illness called
Legionnaires' disease
Legionnaires' disease is a form of atypical pneumonia caused by any species of '' Legionella'' bacteria, quite often '' Legionella pneumophila''. Signs and symptoms include cough, shortness of breath, high fever, muscle pains, and headaches. ...
and a mild flu-like illness called
Pontiac fever
Pontiac fever is an acute, nonfatal respiratory disease caused by various species of Gram-negative bacteria in the genus '' Legionella''. It causes a mild upper respiratory infection that resembles acute influenza. Pontiac fever resolves spontane ...
.
''Legionella'' may be visualized with a
silver stain In pathology, silver staining is the use of silver to selectively alter the appearance of a target in microscopy of histological sections; in temperature gradient gel electrophoresis; and in polyacrylamide gels.
In traditional stained glass, si ...
or cultured in
cysteine
Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile.
When present as a deprotonated catalytic residue, s ...
-containing
media
Media may refer to:
Communication
* Media (communication), tools used to deliver information or data
** Advertising media, various media, content, buying and placement for advertising
** Broadcast media, communications delivered over mass el ...
such as
buffered charcoal yeast extract agar. It is common in many environments, including soil and aquatic systems, with at least 50
species
In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
and 70
serogroups identified. These bacteria, however, are not transmissible from person to person;
furthermore, most people exposed to the bacteria do not become ill. Most outbreaks are traced to poorly maintained
cooling tower
A cooling tower is a device that rejects waste heat to the atmosphere through the cooling of a coolant stream, usually a water stream to a lower temperature. Cooling towers may either use the evaporation of water to remove process heat and ...
s.
The
side chains of the
cell wall
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mec ...
carry the bases responsible for the
somatic antigen A somatic antigen is an antigen located in the cell wall of a gram-positive or gram-negative bacterium.
See also
* Lipopolysaccharide
References
Bacterial proteins
Bacteriology
{{bacteria-stub ...
specificity of these organisms. The chemical composition of these side chains both with respect to components and arrangement of the different sugars determines the nature of the somatic or
O antigen determinants, which are essential means of serologically classifying many gram-negative bacteria.
''Legionella'' acquired its name after
an outbreak in 1976 of a then-unknown "mystery disease" sickened 221 people, causing 34 deaths. The outbreak was first noticed among attendees at a convention of the
American Legion—an association of
U.S. military veterans
A veteran () is a person who has significant experience (and is usually adept and esteemed) and expertise in a particular occupation or field. A military veteran is a person who is no longer serving in a military.
A military veteran that h ...
. The convention occurred in
Philadelphia
Philadelphia, often called Philly, is the largest city in the Commonwealth of Pennsylvania, the sixth-largest city in the U.S., the second-largest city in both the Northeast megalopolis and Mid-Atlantic regions after New York City. Sinc ...
during the
U.S. Bicentennial year on July 21–24, 1976. This epidemic among U.S. war veterans, occurring in the same city as—and within days of the 200th anniversary of—the signing of the
Declaration of Independence
A declaration of independence or declaration of statehood or proclamation of independence is an assertion by a polity in a defined territory that it is independent and constitutes a state. Such places are usually declared from part or all of ...
, was widely publicized and caused great concern in the United States. On January 18, 1977, the causative agent was identified as a previously unknown bacterium subsequently named ''Legionella''.
Detection
''Legionella'' is traditionally detected by culture on buffered charcoal yeast extract agar. It requires the presence of
cysteine
Cysteine (symbol Cys or C; ) is a semiessential proteinogenic amino acid with the formula . The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile.
When present as a deprotonated catalytic residue, s ...
and iron to grow, so does not grow on common blood agar media used for laboratory-based total viable counts or on-site
dipslides. Common laboratory procedures for the detection of ''Legionella'' in water concentrate the bacteria (by centrifugation and/or filtration through 0.2-μm filters) before inoculation onto a charcoal yeast extract agar containing selective agents (e.g. glycine, vancomycin, polymixin, cyclohexamide, GVPC) to suppress other flora in the sample. Heat or acid treatment are also used to reduce interference from other microbes in the sample.
After incubation for up to 10 days, suspect colonies are confirmed as ''Legionella'' if they grow on buffered charcoal yeast extract agar containing cysteine, but not on agar without cysteine added.
Immunological techniques are then commonly used to determine the species and/or serogroups of bacteria present in the sample.
Although the plating method is quite specific for most species of ''Legionella'', one study has shown that a coculture method that accounts for the close relationship with amoebae may be more sensitive, since it can detect the presence of the bacteria even when masked by their presence inside the amoebae. Consequently, the clinical and environmental prevalences of the bacteria are likely to be underestimated due to the current laboratory methodology.
Many hospitals use the ''Legionella'' urinary antigen test for initial detection when ''Legionella'' pneumonia is suspected. Some of the advantages offered by this test are that the results can be obtained in hours rather than the several days required for culture, and that a urine specimen is generally more easily obtained than a sputum specimen. Disadvantages are that the urine antigen test only detects antigen of ''Legionella pneumophila'' serogroup 1 (LP1); only a culture will detect infection by non-LP1 strains or other ''Legionella'' species and that isolates of ''Legionella'' are not obtained, which impairs public health investigations of outbreaks.
New techniques for the rapid detection of ''Legionella'' in water samples have been developed, including the use of
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) ...
and
rapid immunological assays. These technologies can typically provide much faster results.
Government public-health surveillance has demonstrated increasing proportions of drinking water–associated outbreaks, specifically in healthcare settings.
Analyses of genome sequences from ''
Legionellales'' have identified 24
conserved signature indels (CSIs) in diverse proteins including 30S ribosomal protein S8, periplasmic serine endoprotease DegP precursor,
DNA polymerase I, and ABC transporter permease, etc. that are specifically present in different species from the genus ''Legionella''. These molecular signatures provide novel and reliable means for distinguishing members of the genus ''Legionella'' from all other bacteria and for their diagnostics.
Pathogenesis
In the natural environment, ''Legionella'' lives within amoebae such as ''
Acanthamoeba
''Acanthamoeba'' is a genus of amoebae that are commonly recovered from soil, fresh water, and other habitats.
''Acanthamoeba'' has two evolutive forms, the metabolically active trophozoite and a dormant, stress-resistant cyst. Trophozoites are ...
'' spp., ''
Naegleria'' spp., ''Vermamoeba'' spp., or other protozoa such as ''
Tetrahymena pyriformis''.
Upon inhalation, the bacteria can infect
alveolar macrophage
An alveolar macrophage, pulmonary macrophage, (or dust cell) is a type of macrophage, a professional phagocyte, found in the airways and at the level of the alveoli in the lungs, but separated from their walls.
Activity of the alveolar macrophage ...
s, where they can replicate. This results in
Legionnaires' disease
Legionnaires' disease is a form of atypical pneumonia caused by any species of '' Legionella'' bacteria, quite often '' Legionella pneumophila''. Signs and symptoms include cough, shortness of breath, high fever, muscle pains, and headaches. ...
and the less severe illness
Pontiac fever
Pontiac fever is an acute, nonfatal respiratory disease caused by various species of Gram-negative bacteria in the genus '' Legionella''. It causes a mild upper respiratory infection that resembles acute influenza. Pontiac fever resolves spontane ...
. ''Legionella'' transmission is via inhalation of water droplets from a contaminated source that has allowed the organism to grow and spread (e.g., cooling towers). Transmission also occurs less commonly via aspiration of drinking water from an infected source. Person-to-person transmission has not been demonstrated,
though it could be possible in rare cases.
Once inside a host, the incubation period may be up to two weeks.
Prodromal symptoms are flu-like, including fever, chills, and dry cough. Advanced stages of the disease cause problems with the
gastrointestinal
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...
tract and the nervous system and lead to diarrhea and nausea. Other advanced symptoms of pneumonia may also present. However, the disease is generally not a threat to most healthy individuals, and tends to lead to severe symptoms more often in
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 ...
hosts and the elderly. Consequently, the water systems of hospitals and nursing homes should be periodically monitored. The Texas Department of State Health Services provides recommendations for hospitals to detect and prevent the spread of
hospital-acquired disease due to ''Legionella'' infection. According to ''Infection Control and Hospital Epidemiology'', hospital-acquired ''Legionella'' pneumonia has a fatality rate of 28%, and the source is the
water distribution system.
''Legionella'' species typically exist in nature at low concentrations, in groundwater, lakes, and streams. They reproduce after entering man-made equipment, given the right environmental conditions. In the United States, the disease affects between 8,000 and 18,000 individuals a year.
Sources
Documented sources include cooling towers, swimming pools (especially in Scandinavian countries), domestic water systems and showers, ice-making machines, refrigerated cabinets, whirlpool spas, hot springs, fountains, dental equipment, soil, automobile windshield washer fluid, industrial coolant, and waste water treatment plants.
Airborne transmission
The largest and one of the most common source of Legionnaires' disease outbreaks are
cooling tower
A cooling tower is a device that rejects waste heat to the atmosphere through the cooling of a coolant stream, usually a water stream to a lower temperature. Cooling towers may either use the evaporation of water to remove process heat and ...
s (heat rejection equipment used in air conditioning and industrial cooling water systems) primarily because of the risk for widespread circulation. Many governmental agencies, cooling tower manufacturers, and industrial trade organisations have developed design and maintenance guidelines for controlling the growth and proliferation of ''Legionella'' within cooling towers.
Research in the ''Journal of Infectious Diseases'' (2006) provided evidence that ''L. pneumophila'', the causative agent of Legionnaires' disease, can travel at least 6 km from its source by airborne spread. It was previously believed that transmission of the bacterium was restricted to much shorter distances. A team of French scientists reviewed the details of an epidemic of Legionnaires' disease that took place in
Pas-de-Calais
Pas-de-Calais (, " strait of Calais"; pcd, Pas-Calés; also nl, Nauw van Kales) is a department in northern France named after the French designation of the Strait of Dover, which it borders. It has the most communes of all the departments ...
, northern France, in 2003–2004. Of 86 confirmed cases during the outbreak, 18 resulted in death. The source of infection was identified as a cooling tower in a
petrochemical
Petrochemicals (sometimes abbreviated as petchems) are the chemical products obtained from petroleum by refining. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable ...
plant, and an analysis of those affected in the outbreak revealed that some infected people lived as far as 6–7 km from the plant.
Because of these risks, a UK legal mandate requires owners to notify the local authorities of any cooling towers a company operates.
Cooling Tower Notification
Recreational exposure
As outlined above, cooling towers are well established as sources of ''Legionella'' that may have an effect on community exposure to the bacterium and
Legionnaires' disease
Legionnaires' disease is a form of atypical pneumonia caused by any species of '' Legionella'' bacteria, quite often '' Legionella pneumophila''. Signs and symptoms include cough, shortness of breath, high fever, muscle pains, and headaches. ...
epidemics. In addition to cooling towers, use of swimming pools, spa pools, and other recreational water bodies has also been shown to increase risk of exposure to ''Legionella'', though this differs by
species
In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
of ''Legionella''.
In a review of disease caused by recreational exposure to ''Legionella'', most exposures occurred in spas or pools used by the public (hotels or recreational centers) or in natural settings (
hot spring
A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater onto the surface of the Earth. The groundwater is heated either by shallow bodies of magma (molten rock) or by c ...
s or thermal water).
Hotels and other tourist destinations have contributed to ''Legionella'' exposure.
Relative danger at commonly used facilities with heating and cooling water systems depends on several factors, such as the water source, how much ''Legionella'' is present (if there is any), if and how the
water system is treated, how people are interacting with this water, and other factors that make the water systems so dynamic.
In addition to tourists and other
recreators, gardeners may be at increased risk for exposure to ''Legionella''.
In some countries (like Australia), ''Legionella'' lives in soil and compost.
Warmer temperatures and increased rainfall in some regions of the world due to
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
may impact ''Legionella'' in soil, gardeners seasonal exposure to contaminated soil, and complex water systems used by the public.
Exposure related to natural disasters and climate change
Not only are ''Legionella'' spp. present in man-made water systems and infrastructure, but this bacteria also lives in natural bodies of water, such as lakes and rivers.
Weather patterns and other environmental factors may increase risk of ''Legionella'' outbreaks; a study in Minnesota, USA, using outbreak information from 2011 to 2018 showed precipitation as having the greatest effect of increasing risk of ''Legionella'' exposure when taking into account other environmental factors (temperature, relative humidity, land use and age of infected person). Weather patterns heavily relate to the established infrastructure and water sources, especially in
urban settings. In the US, most cases of ''Legionella'' infection have occurred in the summertime, though they were likely more associated with rainfall and humidity than summer temperatures.
Severe rain patterns can increase risk of water source contamination through flooding and unseasonable rains; therefore, natural disasters, especially those associated with climate change, may increase risk of exposure to ''Legionella''.
Vaccine research
No vaccine is available for legionellosis. Vaccination studies using heat-killed or acetone-killed cells have been carried out in guinea pigs, which were then given ''Legionella'' intraperitoneally or by aerosol. Both vaccines were shown to give moderately high levels of protection. Protection was dose-dependent and correlated with antibody levels as measured by
enzyme-linked immunosorbent assay
The enzyme-linked immunosorbent assay (ELISA) (, ) is a commonly used analytical biochemistry assay, first described by Eva Engvall and Peter Perlmann in 1971. The assay uses a solid-phase type of enzyme immunoassay (EIA) to detect the presence ...
to an outer membrane antigen and by indirect
immunofluorescence to heat-killed cells. However, a licensed vaccine is most likely still many years away.
Molecular biology
''Legionella'' has been discovered to be a genetically diverse species with 7-11% of genes strain-specific. The molecular function of some of the proven virulence factors of ''Legionella'' have been discovered.
''Legionella'' control
A biomonitoring solution exists in a ''Legionella''-specific
aptamer-based assay. Control of ''Legionella'' growth can occur through chemical, thermal or ultraviolet treatment methods.
Heat
The more expensive option is temperature control—i.e., keeping all cold water below and all hot water above . The high cost incurred with this method arises from the extensive retrofitting required for existing complex distribution systems in large facilities and the energy cost of chilling or heating the water and maintaining the required temperatures at all times and at all distal points within the system.
Temperature affects the survival of ''Legionella'' as follows:
* Above – ''Legionella'' dies almost instantly
* At – 90% die in 2 minutes (
Decimal reduction time (D) = 2 minutes)
* At – 90% die in 80–124 minutes, depending on strain (
D = 80–124 minutes)
* – can survive but do not multiply
* – ideal growth range
* – growth range
* Below – can survive, even below freezing, but are dormant
Other temperature sensitivity
* to – Disinfection range
* – ''Legionella'' dies within 2 minutes
* – ''Legionella'' dies within 32 minutes
* – ''Legionella'' dies within 5 to 6 hours
Water can be monitored in real-time with sensors.
Chlorine
A very effective chemical treatment is
chlorine
Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is ...
. For systems with marginal issues, chlorine provides effective results at 0.5 ppm residual in the hot water system. For systems with significant ''Legionella'' problems, temporary shock chlorination—where levels are raised to higher than 2 ppm for a period of 24 hours or more and then returned to 0.5 ppm—may be effective. Hyperchlorination can also be used where the water system is taken out of service and the chlorine residual is raised to 50 ppm or higher at all distal points for 24 hours or more. The system is then flushed and returned to 0.5 ppm chlorine prior to being placed back into service. These high levels of chlorine penetrate biofilm, killing both the ''Legionella'' bacteria and the host organisms. Annual hyperchlorination can be an effective part of a comprehensive ''Legionella'' preventive action plan.
Copper-silver ionization
Industrial-sized
copper-silver ionization
Copper-silver ionization is a disinfection process, primarily used to control ''Legionella'', the bacteria responsible for Legionnaires' disease. There is strong evidence that treating water supplies in hospitals with this technique decreases the ...
is recognized by the
U.S. Environmental Protection Agency and WHO for ''Legionella'' control and prevention. Copper and silver ion concentrations must be maintained at optimal levels, taking into account both water flow and overall water usage, to control ''Legionella''. The disinfection function within all of a facility's water distribution network occurs within 30 to 45 days. Key engineering features such as 10 amps per ion chamber cell and automated variable voltage outputs having no less than 100 VDC are but a few of the required features for proper ''Legionella'' control and prevention, using a specific, nonreferenced copper-silver system. Swimming pool ion generators are not designed for potable water treatment.
Questions remain whether the silver and copper ion concentrations required for effective control of symbiotic hosts could exceed those allowed under the U.S. Safe Drinking Water Act's Lead and Copper Rule. In any case, any facility or public water system using copper-silver for disinfection should monitor its copper and silver ion concentrations to ensure they are within intended levels – both minimum and maximum. Further, no current standards for silver in the EU and other regions allow use of this technology.
Copper-silver ionization is an effective process to control ''Legionella'' in potable water distribution systems found in health facilities, hotels, nursing homes, and most large buildings. However, it is not intended for cooling towers because of pH levels greater than 8.6, that cause ionic copper to precipitate. Furthermore,
tolyltriazole, a common additive in cooling water treatment, could bind the copper making it ineffective. Ionization became the first such hospital disinfection process to have fulfilled a proposed four-step modality evaluation; by then, it had been adopted by over 100 hospitals.
[ "(1) Demonstrated efficacy of Legionella eradication in vitro using laboratory assays, (2) anecdotal experiences in preventing legionnaires’ disease in individual hospitals, (3) controlled studies in individual hospitals, and (4) validation in confirmatory reports from multiple hospitals during a prolonged time."] Additional studies indicate ionization is superior to thermal eradication.
Chlorine dioxide
Chlorine dioxide
Chlorine dioxide is a chemical compound with the formula ClO2 that exists as yellowish-green gas above 11 °C, a reddish-brown liquid between 11 °C and −59 °C, and as bright orange crystals below −59 °C. It is usually ...
has been approved by the U.S.
Environmental Protection Agency
A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale f ...
as a primary disinfectant of
potable water
Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, ...
since 1945. Chlorine dioxide does not produce any carcinogenic byproducts like chlorine when used in the purification of drinking water that contains natural organic compounds such as humic and fulvic acids; chlorine tends to form halogenated disinfection byproducts such as
trihalomethane
In chemistry, trihalomethanes (THMs) are chemical compounds in which three of the four hydrogen atoms of methane () are replaced by halogen atoms. Many trihalomethanes find uses in industry as solvents or refrigerants. THMs are also environm ...
s. Drinking water containing such disinfection byproducts has been shown to increase the risk of cancer. ClO
2 works differently from chlorine; its action is one of pure oxidation rather than halogenation, so these halogenated byproducts are not formed.
Chlorine dioxide is not a restricted heavy metal like copper. It has proven excellent control of ''Legionella'' in cold and hot water systems and its ability as a biocide is not affected by pH, or any water corrosion inhibitors such as silica or phosphate. However, it is 'quenched' by metal oxides, especially manganese and iron. Metal oxide concentrations above 0.5 mg/L may inhibit its activity.
Monochloramine is an alternative. Like chlorine and chlorine dioxide, monochloramine is approved by the Environmental Protection Agency as a primary potable water disinfectant. Environmental Protection Agency registration requires a biocide label which lists toxicity and other data required for all registered biocides. If the product is being sold as a biocide, then the manufacturer is legally required to supply a biocide label, and the purchaser is legally required to apply the biocide per the biocide label. When first applied to a system, chlorine dioxide can be added at disinfection levels of 2 ppm for 6 hours to clean up a system. This will not remove all biofilm, but will effectively remediate the system of ''Legionella''.
Moist heat sterilization
Moist heat sterilization (
superheating
In thermodynamics, superheating (sometimes referred to as boiling retardation, or boiling delay) is the phenomenon in which a liquid is heated to a temperature higher than its boiling point, without boiling. This is a so-called ''metastable sta ...
to and flushing) is a nonchemical treatment that typically must be repeated every 3–5 weeks.
Ultraviolet
Ultraviolet light, in the range of 200 to 300 nm, can inactivate Legionella. According to a review by the US EPA, three-log (99.9%) inactivation can be achieved with a dose of less than 7 mJ/cm
2.
Biomonitoring
A ''Legionella''-specific
aptamer has been discovered and in 2022 was developed into an assay for detecting to a limit of 10
4.3 cells/mL with no processing steps.
European standards
Several European countries established the
European Working Group for Legionella Infections The European Working Group for Legionella Infections (EWGLI) was formed in 1986. Its members are scientists with an interest in improving knowledge and information on the epidemiological and microbiological (clinical and environmental) aspects of le ...
to share knowledge and experience about monitoring potential sources of ''Legionella''. The working group has published guidelines about the actions to be taken to limit the number of colony-forming units (that is, live bacteria that are able to multiply) of ''Legionella'' per litre:
Monitoring guidelines are stated in Approved Code of Practice L8 in the UK. These are not mandatory, but are widely regarded as so. An employer or property owner must follow an Approved Code of Practice, or achieve the same result. Failure to show monitoring records to at least this standard has resulted in several high-profile prosecutions, e.g. Nalco + Bulmers – neither could prove a sufficient scheme to be in place while investigating an outbreak, therefore both were fined about £300,000GBP. Important case law in this area is R v Trustees of the Science Museum 3 All ER 853, (1993) 1 WLR 1171
Employers and those responsible for premises within the UK are required under Control of Substances Hazardous to Health to undertake an assessment of the risks arising from Legionella. This risk assessment may be very simple for low risk premises, however for larger or higher risk properties may include a narrative of the site, asset register, simplified schematic drawings, recommendations on compliance, and a proposed monitoring scheme.
The L8 Approved Code of Practice recommends that the risk assessment should be reviewed at least every 2 years and whenever a reason exists to suspect it is no longer valid, such as water systems have been amended or modified, or if the use of the water system has changed, or if there is reason to suspect that Legionella control measures are no longer working.
Weaponization
''Legionella'' could be used as a weapon, and indeed genetic modification of ''L. pneumophila'' has been shown where the mortality rate in infected animals can be increased to nearly 100%.
A former Soviet bioengineer,
Sergei Popov, stated in 2000 that his team experimented with genetically enhanced
bioweapons, including ''Legionella''.
[ Popov worked as a lead researcher at the Vector Institute from 1976 to 1986, then at Obolensk until 1992, when he defected to the West. He later divulged much of the ]Soviet biological weapons program
The Soviet Union covertly operated the world's largest, longest, and most sophisticated biological weapons program, thereby violating its obligations as a party to the 1972 Biological Weapons Convention.Leitenberg, M., Zilinskas, R., & Kuhn, J. ...
and settled in the United States.
See also
* Environmental microbiology
* List of Legionnaires' disease outbreaks
This is a list of Legionnaires' disease outbreaks; Legionnaire's is a potentially fatal infectious disease caused by gram negative, aerobic bacteria belonging to the genus ''Legionella''. The first reported outbreak was in Philadelphia, Pennsylvan ...
* Microbiomes of the built environment
References
External links
European Working Group for Legionella Infections
Centers for Disease Control and Prevention
€”Procedure for Cleaning Cooling Towers and Related Equipment (pages 239 and 240 of 249)
California Energy Commission
€”Cooling Water Management Program Guidelines For Wet and Hybrid Cooling Towers at Power Plants
ASHRAE Guideline
* ttps://web.archive.org/web/20080611231131/http://www.hse.gov.uk/pubns/iacl27.pdf Employers Guidelines for prevention of ''Legionella''
{{Authority control
Bacteria genera
Bacterial diseases
Gram-negative bacteria
Industrial hygiene
Legionellales
Pathogenic bacteria