Legionella is a type of bacterium found naturally in freshwater environments, like lakes and streams. It can become a health concern when it grows and spreads in human-made building water systems like:

  • Showerheads and sink faucets
  • Cooling towers (structures that contain water and a fan as part of centralized air cooling systems for building or industrial processes)
  • Decorative fountains and water features
  • Hot water tanks and heaters
  • Large plumbing systems

Many businesses are closed during the COVID-19 outbreak. Stagnant, or standing, water can cause conditions that increase risk for Legionella and other biofilm-associated bacteria.

Fast Facts from the Centers for Disease Control and Prevention:

  • Legionella can cause Legionnaires’ disease, Pontiac fever, and, more rarely, extrapulmonary infections, collectively known as legionellosis.
  • Scientists named the bacterium after an outbreak in Philadelphia in 1976. During that outbreak, many people who went to an American Legion convention got sick with pneumonia (lung infection).
  • Health departments reported nearly 10,000 cases of Legionnaires’ disease in the United States in 2018. However, because Legionnaires’ disease is likely underdiagnosed, this number may underestimate the true incidence.
  • About one in 10 people who gets sick from Legionnaires’ disease will die.
  • People can get Legionnaires’ disease or Pontiac fever when they breathe in small droplets of water in the air that contain Legionella.
  • In general, people do not spread Legionnaires’ disease to other people. However, this may be possible under rare circumstances.
  • Legionella occurs naturally in fresh water environments, like lakes and streams. It can become a health concern when it grows and spreads in human-made building water systems.
  • Keeping Legionella out of water systems in buildings is key to preventing infection.