Flesh-Eating Bacteria at the Beach? What You Need to Know.

The Back Story: An infection that surprises beachgoers.

It’s not clear whether the appearance of these cases farther north than usual may be a result of better diagnosis or to warming waters associated with climate change.

The illness, technically called vibriosis, may be caused by infection with several related bacteria. Among the worst is V. vulnificus, which is relatively rare but can be deadly for those who are vulnerable, with survival rates as low as 33 percent, according to one scientific paper.

The bacterium spreads most commonly in two ways.

When people swim in waters contaminated with V. vulnificus, an open sore or cut can provide an entry point for the organism. From there it spreads, becoming a so-called flesh-eating infection that extends quickly beyond the wound into healthy tissue. Then it may spill over into the bloodstream, causing a life-threatening condition called sepsis.

The bacterium also spreads when people who are immunocompromised or have liver disease eat raw oysters that are contaminated. Physicians warn patients with these conditions against eating raw oysters, which become infected by seawater they filter for food.

Older people are generally at greater risk. The three patients who fell ill in Connecticut were all over age 60. People who take medications to reduce stomach acid may also be more likely to get infected or to develop complications following infection.

If you’re among the vulnerable, wear shoes that protect against cuts and scrapes when you’re in salty or brackish water. Wear protective gloves when handling raw seafood. Avoid swimming in the ocean if you have a cut, scrape or other abrasion that might let in the bacterium.

What to Watch: The bacterium seizes on openings.

Vibriosis causes a wide range of symptoms, including diarrhea and stomach cramps, vomiting, fever, chills, ear infections and wound infections.

The intestinal problems occur more quickly in people who have ingested the bacterium, usually by eating raw oysters. Ear and wound infections will become red, swollen and extremely painful over a bit more time. Blisters filled with clear liquid may appear on the skin.

Symptoms usually appear within 12 to 24 hours of exposure, and people should seek medical care as soon as possible. Tell doctors about the exposure: The infection can spread quickly if left untreated.

“If the wound starts to look red, puffy and painful, or has a discharge, or redness spreading beyond the edges of the wound, you need to get medical attention right away,” Dr. Schaffner said. “Don’t try to tough it out and wait to see if it gets worse tomorrow.”

A lab test is needed to make the diagnosis. Treatment involves antibiotics and supportive care, but surgery may be required to clean out an infected wound and stop the spread of the infection.

Your Beach Weekend: The vulnerable should exercise caution.

Consider avoiding the water, and not even walking on the beach or wading, if you have an open wound, including one from a recent surgical operation or piercing or tattoo. An open wound means any cut, scrape or other abrasion that might allow the bacterium into your body.

If there is a chance your wound could come into contact with saltwater or brackish water, marine life, or raw or undercooked seafood while you’re cooking, swimming, fishing, boating or walking on the beach, cover the open wound with a waterproof bandage.

If a wound or cut does comes into contact with brackish water or saltwater, raw seafood or its juices, wash it thoroughly with soap and water. If you develop a skin infection, let your health provider know quickly — this is an infection that can spread rapidly.

What’s Next: Watch for the infection in unexpected places.

Climate change will test all of us in unexpected ways. Vibrio infection is something Americans living in the Northeast may need to watch for now.

If you have cancer, are immunocompromised, have liver disease or take drugs to lower stomach acid, doctors say you should not eat raw or undercooked oysters or other raw or undercooked shellfish. (Of course, the same is true for pregnant women.)

If you’re handling raw shellfish, wash your hands thoroughly with soap and water afterward.