In North Carolina, officials recorded 310 cases of Legionnaires' disease in 2025, a 54% increase from the previous year. Nationwide in the US, infections have increased nearly 1,000% over two decades, from 1,100 cases in 2000 to over 8,000 today. The reasons for the spike in North Carolina remain unclear, and it is unknown whether any patients there were hospitalized or died, how they were infected, or the potential source of the bacteria.
Recent outbreaks have emerged elsewhere, with Ector County, Texas, officials detecting 12 Legionnaires' disease cases and two deaths between late December and early January. In London, the UK Health Security Agency (UKHSA) is investigating a cluster of cases linked to north-west and south-west London. A common source for the London cases has not yet been confirmed, according to the UKHSA.
Around 300 cases of Legionnaires' disease are reported each year in England and Wales. In Baltimore, Maryland, politicians have alleged that Legionella bacteria caused an outbreak this month at a federal building housing ICE detainees. The exact number of cases and deaths in this alleged outbreak has not been disclosed.
Legionnaires' disease is a severe form of pneumonia caused by Legionella bacteria. It is spread through contaminated water vapor or fine water droplets containing Legionella bacteria. Legionella bacteria thrive in warm, moist, or stagnant water environments, such as air conditioning units, hot tubs, plumbing systems, and large water systems.
People most at risk from Legionnaires' disease include those over 50, smokers, former smokers, and people with lung conditions or weakened immune systems. Legionnaires' disease is usually treated in hospitals with antibiotics. Legionnaires' disease is uncommon but can be serious.
Health experts warn that warmer temperatures are allowing Legionella bacteria to thrive, raising infection risks. The disease's spread through water systems highlights the need for monitoring and prevention efforts.