NJ officials investigate unusual spike in Legionnaires' disease

a magnetized image of the bacteria that cause Legionnaires' disease, which are rod-shaped and depicted in pink
The bacteria behind Legionnaires' disease (pictured) can grow in various building water systems. (Image credit: Janice Haney Carr)

An unexpected surge in cases of Legionnaires' disease in two New Jersey counties has prompted the state health department to launch an investigation.

People catch Legionnaires' disease, a serious bacterial lung infection, after swallowing or inhaling water droplets that contain Legionella bacteria. The infection can't spread from person to person.

Legionella bacteria live in freshwater environments, such as lakes, but they can also grow in human-made water systems, such as hot-water tanks, cooling towers and showerheads. Most healthy people exposed to Legionella don't fall ill, but the disease can strike people ages 50 and older, those with a history of smoking, and those with chronic lung disease, weakened immune systems, cancer or diabetes.

Between August and early November, the New Jersey Department of Health (NJDOH) learned of 41 cases of Legionnaires' in two counties: 21 people in Middlesex County became sick and tested positive for Legionella, as did 20 in Union County. No deaths have been reported.

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"On average, each of these counties receives six to eight confirmed reports of Legionnaires' disease from August to October each year," so the recent bump in cases is unusual, the NJDOH noted in a statement.

"NJDOH is actively collaborating with local health departments in Middlesex and Union counties to investigate these cases and any potential sources of infection," the statement said. "In mid-October, NJDOH alerted local health departments, health care providers, and other public health partners in the area regarding the elevated number of reported cases. To date, a common exposure among cases has not been identified."

Symptoms of Legionnaires' disease — such as fever, chills, cough, shortness of breath, chest pain and muscle aches — can take up to two weeks to emerge, according to the NJDOH. People who develop such symptoms within two weeks of visiting Middlesex or Union county should seek medical attention, the department recommended.

"Early diagnosis is key to effectively treating Legionnaires' disease," which can be treated with antibiotics, Dr. Kaitlan Baston, acting health commissioner, said in the statement. "Although the risk of contracting Legionnaires' disease if you live in or have recently visited Middlesex or Union counties remains low, individuals who develop pneumonia-like respiratory symptoms should visit their health care provider immediately to be evaluated."

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Nicoletta Lanese
Channel Editor, Health

Nicoletta Lanese is the health channel editor at Live Science and was previously a news editor and staff writer at the site. She holds a graduate certificate in science communication from UC Santa Cruz and degrees in neuroscience and dance from the University of Florida. Her work has appeared in The Scientist, Science News, the Mercury News, Mongabay and Stanford Medicine Magazine, among other outlets. Based in NYC, she also remains heavily involved in dance and performs in local choreographers' work.