(NewsNation) — This Fourth of July weekend, health experts have a warning before you head into the water. A potentially deadly bacteria once found mostly along the Gulf Coast is now being detected farther north, including in several waterways of New York’s Long Island.

For most healthy beachgoers, the risk remains low. But for people with certain health conditions, or even a small open wound, an infection can quickly become life-threatening.

The bacteria, called Vibrio vulnificus, naturally lives in warm salt and brackish water, where fresh water and saltwater mix. It can enter the body through an open cut or by eating raw or undercooked shellfish, especially oysters.

Researchers this spring found the bacteria in multiple Long Island waterways, and officials in the Hamptons posted an alert about the findings.

In Florida, health officials reported eight cases this year as of early June, compared with five during the same period last year. Mississippi health officials also issued a warning in June, urging people to take precautions.

The warning comes after a South Mississippi man was hospitalized with a severe Vibrio infection, according to the Sun Herald. Steve Wilson’s wife told the outlet they were fishing when he noticed what appeared to be a horsefly bite on his foot. They initially dismissed it, but the next day his leg became extremely painful, and the infection spread quickly. He remains in critical condition as doctors work to save his life.

“It is pretty much a life-threatening infection, but also it’s a surgical and medical emergency,” Dr. Carlos Arias of Encompass Health said.

Despite its nickname, the bacteria do not literally eat flesh. However, it can destroy tissue and spread into the bloodstream with alarming speed. According to the Centers for Disease Control and Prevention, about one in five people infected with Vibrio die, sometimes within just one or two days of becoming sick.

Health experts said the best protection is simple: Avoid entering warm costal water if you have an open wound. That includes recent surgical incisions, piercings or tattoos or even small cuts.

People with liver disease, diabetes, cancer or weakened immune systems face the highest risk of severe illness.

Anyone who develops redness, swelling, severe pain, blisters or rapidly worsening symptoms after exposure to seawater should seek medical care immediately. The CDC recommends doctors begin treatment as soon as a Vibrio wound infection is suspected, without waiting for lab results.

Experts have also raised concerns that reductions to some federal monitoring programs could make emerging threats harder to track.

The Trump administration has said the CDC continues to monitor Vibrio through other national systems.

Before heading to the beach, health experts urge people to check their skin for cuts, keep wounds covered, thoroughly cook shellfish and never ignore an infection that appears to be worsening rapidly.

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