According to the CDC, cases of Legionnaires’ disease in the U.S. have tripled in the last decade, though the risk of dying from the disease is lower due to improved treatment methods.
The year 2009 saw 3,522 reported cases of Legionnaires’ disease, compared to 1,110 in 2000. The Centers for Disease Control hold doctors and hospitals responsible to report cases of Legionnaires’ disease they diagnose, as do many state laws. Due to its similarity to pneumonia, however, Legionnaires’ disease often goes unrecognized, undiagnosed, and therefore unreported; experts estimate that there are thousands more Americans every year who are sickened with Legionnaires’ disease, but whose cases are overlooked.
For the same reason, it is possible that the apparent rise of Legionnaires’ disease cases can be attributed to an increase in the frequency of cases reported; in other words, it is not that more cases are occurring, just that more are being reported and documented.