You’ve likely stumbled across one of several recent news stories describing cases of necrotizing fasciitis, or “flesh-eating bacteria.” The condition can follow exposure to certain bacteria in public beaches, pools, or rivers. This July, a man in Okaloosa County, Florida with a compromised immune system died after going into local waters. Just two weeks before, a 12-year-old girl was diagnosed with necrotizing fasciitis after scraping her foot in Pompano Beach, Florida. The stories and their disturbing imagery spread on social media, inviting questions over the condition and how it can be avoided.

According to the Centers for Disease Control and Prevention, necrotizing fasciitis can be caused by different strains of bacteria, with group A Streptococcus (strep) being the most common. When group A strep enters the body through a break in the skin like a cut or burn, a serious and rapidly spreading infection can develop. People will have a high fever, severe pain at the site of exposure, and eventual tissue destruction, which gives the condition its name. Necrotizing is to cause the death of tissue, while fasciitis is 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 are all used in an attempt to resolve the infection.

Even with care, necrotizing fasciitis can lead to complications like organ failure or sepsis. An estimated one in three people who are diagnosed with the condition die.

Fortunately, the condition is extremely 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 low estimate.

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 and rivers 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, unfortunately. A recent study in the Annals of Internal Medicine suggested that warmer water temperatures in Delaware Bay has allowed another kind of bacteria, Vibrio vulnificus, to flourish, resulting in five cases of necrotizing fasciitis in 2017 and 2018. Previously, only one case had been confirmed since 2008. Florida is also known to harbor group A strep in seawater.

But, owing to its rarity, necrotizing fasciitis should not overly concern people with healthy immune systems and unbroken skin. If you suffer a cut with a reddened area accompanied by severe pain and fever, however, seek medical evaluation right away.