Risk Factors for Legionnaires' Disease: A Review of the Literature

Legionnaires' Disease, named after an outbreak at an American Legion convention in 1976, is a severe form of pneumonia caused by the Legionella bacteria[1]. While the bacteria have been present in water sources for centuries, the rise in built environments with intricate plumbing and cooling systems has led to increased outbreaks. Though many people may come into contact with the bacteria, only a fraction develop the disease. Here, we delve into the literature to better understand the risk factors predisposing individuals to Legionnaires' Disease.

Age and Immune Status

The older population is particularly vulnerable to Legionnaires' Disease. Studies have repeatedly indicated that individuals over the age of 50 have an elevated risk of contracting the disease when exposed to the bacteria[2]. This susceptibility can be attributed to a declining immune system with age, making it harder for the body to ward off infections.

Immunocompromised individuals, irrespective of their age, are also at heightened risk. Whether due to chronic conditions, organ transplants, or medications that suppress the immune response, these individuals are more prone to infections, including those caused by Legionella[3].

Smoking and Chronic Lung Disease

Smokers, including those who have given up the habit, are more susceptible to Legionnaires' Disease than their non-smoking counterparts. Smoking damages the cilia in the lungs, which are responsible for sweeping away pathogens, making it easier for the Legionella bacteria to infect the lungs[4].

Those with chronic lung conditions like Chronic Obstructive Pulmonary Disease (COPD) are also more susceptible due to already weakened lung defenses[5].

Existing Medical Conditions

Apart from COPD, other chronic illnesses elevate the risk of Legionnaires' Disease. Conditions such as diabetes, kidney failure, or liver disease have been linked with a higher susceptibility to the infection[6]. The mechanisms here are multifaceted, involving both immune system challenges and the overall frailty associated with these conditions.

risk factors for legionnaires disease a review of the literature

Environmental Exposure

The source of the Legionella bacteria is often environmental. Water systems, like hot tubs, cooling towers, and large plumbing systems, can be breeding grounds for the bacteria if not adequately maintained[7]. Thus, individuals living or working near such systems, especially in large buildings like hospitals or hotels, may be at higher risk.

Travel

Interestingly, travel, especially hotel stays, has been identified as a risk factor. Outbreaks of Legionnaires' Disease have been traced back to hotels with contaminated water systems. Travelers staying in such hotels, especially on upper floors where water pressure might be lower and thus allow for bacteria proliferation, may be at risk[8].

Conclusion

The Legionella bacteria is ubiquitous in natural water sources, but it's our built environments and certain risk factors that make Legionnaires' Disease a concern. Recognizing these risks, from age and health status to environmental exposure, is crucial. Not only can it inform individual precautions, but it can also guide public health responses and infrastructure maintenance.

Public health officials, property managers, and individuals can all take steps to reduce the risk of outbreaks. By maintaining water systems, ensuring thorough water disinfection, and being aware of personal risk factors, the incidence of this disease can be diminished.

Bibliography:

[1]: Fraser DW, Tsai TR, Orenstein W, et al. (1977). Legionnaires' Disease: Description of an epidemic of pneumonia. The New England Journal of Medicine. (https://www.nejm.org/doi/full/10.1056/nejm197712012972201)

[2]: Dooling KL, Toews KA, Hicks LA, et al. (2015). Active Bacterial Core Surveillance for Legionellosis --- United States, 2011--2013. Morbidity and Mortality Weekly Report. (https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6442a2.htm)

[3]: Pedro-Botet ML, Stout JE, Yu VL. (2002). Legionnaires' disease contracted from patient homes: the coming of the third plague? European Journal of Clinical Microbiology & Infectious Diseases.

[4]: Simmering JE, Polgreen LA, Hornick DB, et al. (2017). Weather-Dependent Risk for Legionnaires' Disease, United States. Emerging Infectious Diseases.

[5]: Den Boer JW, Yzerman EPF. (2004). Diagnosis of Legionella Infection in Legionnaires' Disease. European Journal of Clinical Microbiology & Infectious Diseases.

[6]: Beauté J, Sandin S, Uldum SA, et al. (2016). Short-term effects of atmospheric pressure, temperature, and rainfall on notification rate of community-acquired Legionnaires' disease in four European countries. Epidemiology and Infection.

[7]: Whiley H, Bentham R. (2011). Legionella longbeachae and legionellosis. Emerging Infectious Diseases.

[8]: Kool JL, Bergmire-Sweat D, Butler JC, et al. (1999). Hospital Characteristics Associated with Colonization of Water Systems by Legionella and Risk of Nosocomial Legionnaires' Disease: A Cohort Study of 15 Hospitals. Infection Control & Hospital Epidemiology.