As the world starts to recover from the ongoing COVID-19 pandemic, scientists are worried that people returning to the workplace could be exposed to another dangerous pathogen that thrives in warm, stagnant water in the pipes of long-dormant buildings: Legionella.
What is Legionella?
Legionella is the genus of bacteria that causes Legionnaires’ disease, a potentially fatal form of pneumonia (lung infection), and the less severe, flu-like Pontiac fever, named for the Michigan town where it was first described. The former got its name from a pneumonia outbreak that occurred at an American Legion convention in Philadelphia in 1976, which infected over 180 people and resulted in at least 29 deaths. Legionnaires’ disease can also cause fever, cough, muscle pain and headaches.
Incidents of Legionnaires’ disease have been rising steadily over the last two decades. Close to 10,000 people were diagnosed with the disease in the United States in 2018, though the CDC suggests the number of cases is likely much higher because many people with pneumonia are not tested for Legionella infection. In response to this trend, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) developed Standard 188: Legionellosis: Risk Management for Building Water Systems in 2015.
How is Legionnaires’ disease transmitted?
Both illnesses are contracted when small droplets of water in the air that contain Legionella bacteria are breathed in or, less commonly, when water accidentally goes into the lungs while drinking. Legionella is not generally spread from one person to another.
Where is Legionella found?
Safe amounts of Legionella can be found in natural freshwater environments, like lakes and streams, but the bacteria can grow to dangerous levels in man-made water systems, including showerheads, cooling towers and plumbing systems. Mismanagement of these systems can put people at risk of contracting Legionnaires’ disease or Pontiac fever.
How does Legionella contamination happen?
In a building’s water system, Legionella bacteria grow in biofilms, collections of microorganisms stuck together with extracellular polymeric substances (EPS), that grow on the surfaces of infrastructure. This is why it’s important to include general microbial monitoring and specific Legionella detection for a complete Legionella monitoring plan.
Who’s susceptible to Legionnaires’ disease?
Anyone who is exposed to Legionella can contract Legionnaires’ disease or Pontiac fever but certain groups, including older people, smokers, those with weak immune systems or chronic lung diseases and those working in close proximity to large air-conditioning systems, are at higher risk.
Symptoms of Legionnaires’ disease typically develop two to 10 days after exposure to the bacteria. Those who develop pneumonia symptoms should see a doctor right away and be sure to mention any suspected exposure to Legionella. Symptoms of Pontiac fever can begin within a few hours to three days of exposure and usually last less than a week.