After stable numbers for more than a decade, reported Legionnaires' disease cases have been rising since 2003 in the U.S., according to a CDC report released Feb. 17.
Legionnaires' disease is contracted when water droplets containing Legionella bacteria are inhaled. About 10 percent of people who contract Legionnaires' die, according to the CDC.
Six things to know:
1. CDC researchers compared patterns associated with cases reported to the CDC before and during the rise. From 1992-2002, they found an average of 1,221 cases reported each year, compared to an average of 4,369 cases reported annually during 2003-18. The age-standardized average incidence was 0.48 cases for every 100,000 Americans during 1992-2002, compared to 2.71 cases per 100,000 in 2018.
2. During both periods, the largest number of cases occurred among white people, but the highest incidence was in Black people.
3. Case increases were generally largest in East North Central, Middle Atlantic and New England regions.
4. Rising incidence was most significantly linked to increasing racial disparities, geographic region and seasonality.
5. Almost two-thirds of Legionnaires' disease cases have no known cause, but better water management can reduce risk in buildings with complex water systems.
6. It's unclear what effect, if any, the COVID-19 pandemic and pandemic-associated issues have had on Legionnaires' disease cases.