Legionnaires' disease is caused by the bacterium, Legionella. The bacterium was named after an outbreak in 1976, when many people who went to a Philadelphia convention of the American Legion got sick with pneumonia.

In the United States, approximately 5,000 cases of Legionnaires' disease are reported annually. However, Legionnaires' disease is likely underdiagnosed and the true numbers are likely higher.

I was joined by two experts on Legionnaires' disease, Legionella and water systems–civil engineering/environmental engineer and the Charles P. Lunsford Professor of Civil and Environmental Engineering at Virginia Tech, Dr. Marc Edwards and scientist and engineer, Sarah Ferrari, who is a member of the Alliance to Prevent Legionnaires' Disease, a coalition of subject matter experts and stakeholders formed to promote best practices on Legionnaires' Disease prevention.