Stay Safe from Lethal Legionella Bacteria

Perhaps you remember back to the American bicentennial celebration in July 1976, when thousands of members of the American Legion arrived to celebrate in Philadelphia, whereupon hundreds got sick and 34 people died from the severe lung infection that came to be known as Legionnaires’ disease. It is a form of pneumonia contracted by inhaling Legionella bacteria, which thrive in warm water found in plumbing systems, whirlpool spas, cooling towers and showers.

Lately there has been a steep rise in the number of cases, according to figures released by the Centers for Disease Control and Prevention. Preeta Kutty, MD, a CDC medical epidemiologist, confirms that between 8,000 and 18,000 people are hospitalized with Legionnaires’ disease in the US each year, with the number of reported cases up 217% from 1,110 in 2000 to 3,522 in 2009 (the most recent data available). The reason for the increase remains unclear—Dr. Kutty speculates it might relate to climate conditions that enable the bacteria that cause the disease to thrive, or it might be that diagnosis and reporting have improved. Even so, she said she believes that the disease remains both underdiagnosed and underreported.


Legionnaires’ disease resembles other forms of pneumonia, with symptoms such as high fever, chills, coughing, muscle aches and headaches appearing two to 14 days after exposure to the bacteria. It’s a serious illness, causing death in 5% to 30% of cases. Older people, smokers, people with chronic lung disease and those with weakened immune systems are particularly susceptible to infection and at greatest risk for complications. A milder form of the disease is known as Pontiac fever—collectively, Legionnaires’ disease and Pontiac fever are often referred to as legionellosis.

Legionella bacteria enter the body via inhalation of contaminated water droplets in the air—for example, through air-conditioning systems in large buildings or whirlpool spas that have not been properly cleaned and disinfected. Another source of infection is by drinking contaminated water. Treatment is with antibiotics.


Large-scale environments such as hotels or ships or hospitals are most likely to have Legionella lurking somewhere in their systems, but the bacteria can also be found in apartment building and hotel cooling towers…garden ponds and fountains…water heaters…and sometimes even in freshwater ponds and creeks. Dr. Kutty advises people at greatest risk to take precautions to limit exposure, especially when traveling or in a medical facility. Her advice includes…

• Limit exposure to public hot tubs. Studies have shown that these are one of the prime culprits in the spread of Legionnaires’ disease.

• Beware of long, hot, steamy showers—especially in big buildings, such as apartments or hotels, which are more likely to harbor Legionella bacteria. The best defense is to make sure that water heaters bring temperatures above 140ºF.

• Follow a healthful lifestyle. A robust immune system is your best protection against Legionnaires’ as well as other diseases.

• If you are immune-compromised and therefore especially vulnerable to such infections, talk to your health-care provider about how to avoid infection. This is one more illness you don’t need to get.