Louisiana health officials are urging residents to take precautions against a flesh-eating bacterial infection following the deaths of five people this year.

The Louisiana Department of Health issued a warning about the infection, known as Vibrio vulnificus, in a press release on Thursday.

The department said nine people have been infected this year and five have died. By comparison, Louisiana averaged seven cases and one death annually over the previous 10 years during the same time period.

All of this year’s reported cases were linked to wounds exposed to seawater, and all patients had underlying health conditions, the department added.

Vibrio bacteria naturally live in coastal waters, according to the Centers for Disease Control and Prevention, and is more common in the summer when water temperatures rise.

People can contract the infection by eating raw or undercooked shellfish, particularly oysters, or when an open wound comes into contact with coastal waters, the CDC says.

About 1 in 5 people with a Vibrio vulnificus infection die, according to the agency.

While anyone can be infected, the Louisiana Department of Health said those most at risk include people with liver disease, cancer, diabetes, HIV or thalassemia; people undergoing immune-suppressing treatment; people taking medication that reduces stomach acid; and people who recently had stomach surgery.

Symptoms include watery diarrhea, stomach cramps, nausea, vomiting, fever and chills, according to the CDC.

The department urged residents to seek medical care immediately if a wound exposed to brackish or salt water becomes red, swollen, painful, warm or discolored, and to tell their health care provider about the water exposure.

Louisiana saw a similar spike in Vibrio infection last year, with at least 17 cases were reported in the state. At least 10 people in Florida, Louisiana and the Outer Banks of North Carolina died from the infection last year, according to health officials.