You’ve likely stumbled across one of several recent news stories describing cases of necrotizing fasciitis caused by flesh-eating bacteria. The condition can follow exposure to certain bacteria in public beaches, pools, or rivers. In August 2023, three people in New York and Connecticut died after coming into contact with Vibrio vulnificus, a bacterium found in warm seawater and in shellfish. With more people swimming in lakes and seashores in summer, and with some of the warmest ocean surface temperatures ever recorded this year, your chances of exposure to flesh-eating bacteria may be increasing.

According to the CDC, necrotizing fasciitis can be caused by different strains of bacteria, with group A Streptococcus being the most common. When group A strep enters the body through an open cut or burn, a serious and rapidly spreading infection can develop. People will have a high fever, severe pain, and eventual tissue death around the site of the infection, which gives the condition its name. (Necrotizing means to cause the death of tissue, and fasciitis describes inflammation of the fascia, or tissue under the skin.)

Because necrotizing fasciitis spreads so quickly, it’s crucial for people to seek medical attention immediately if they see early symptoms: rapid swelling and redness that spreads from a cut or burn, fever, and severe pain. Doctors can diagnose the infection using tissue biopsies, blood work, or imaging of the infected site, though they’ll almost always initiate treatment immediately. IV antibiotics, surgery to excise dead tissue, and blood transfusions may be used to get the infection under control.

Even with medical care, necrotizing fasciitis can lead to organ failure or sepsis. About 20 percent (one in five) people who experience necrotizing fasciitis die, and the rate is even higher for people who develop complications.

Fortunately, the condition is rare in the United States, with an estimated 700 to 1200 cases confirmed each year. The CDC acknowledges, however, that the number is likely an undercount.

Because group A strep can be found in water, the CDC advises people to avoid going into public waters with any kind of open wound. This applies to both public beaches, rivers, and lakes as well as swimming pools or hot tubs. Chlorination is no guarantee against group A strep. Any cut or other wound should always be cleaned with soap and water. It’s especially important that people with compromised immune systems from illness, diabetes, cancer, or another conditions be exceedingly careful.

Rising ocean temperatures may make necrotizing fasciitis more common. A 2023 study in the journal Scientific Reports suggested that warmer water temperatures in the coming decades may result in Vibrio vulnificus infections occurring in ever U.S. state on the eastern seaboard.

But, owing to its rarity, necrotizing fasciitis should not overly concern people with healthy immune systems and unbroken skin. But if you end up with wound surrounded by reddened tissue and severe pain on your summer vacation, seek medical evaluation right away.

A version of this story was published in 2021; it has been updated for 2023.

This article was originally published on www.mentalfloss.com as What You Should Know About Necrotizing Fasciitis, the Flesh-Eating Bacterial Infection.