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July 3, 2019 -- Vibriosis, an infection that is often mild but can turn lethal, may be a bigger threat this summer than usual as experts report the bacteria that cause the infection are showing up in unusual places.

The infection is caused by about a dozen species of vibrio bacteria, the CDC says. One, Vibrio vulnificus, is common along the Southeastern U.S. coast. But experts have found it has migrated farther north, to Delaware Bay, which has slightly cooler waters than the usual locations.

Researchers recently reported five cases of the infection from summer 2017 through fall 2018, all from Delaware Bay. Three patients were crabbing in the bay, one had workplace exposure to shellfish from the bay, and one had an open wound while cleaning and eating crabs. One patient died. The state of Delaware has not had any reports of Vibrio vulnificus this year, says Jen Brestel, a spokesperson for the Delaware Department of Health and Social Services, although there have been 6 reports of other Vibrio species infections so far in 2019.

(The cases Vibrio vulnificus cases reported from the Delaware Bay, she says, involved non-Delaware residents.)

The bacteria can lead to serious and sometimes lethal skin infections or food poisoning. If it causes serious food poisoning, you may need to be hospitalized. If it causes a severe skin infection, it can become necrotizing fasciitis, commonly known as ''flesh-eating bacteria," and you may need an amputation.

As for 2019, "we haven't seen any cases yet, but it is early in the season," says Katherine Doktor, MD, assistant professor of infectious diseases at Rowan University, who co-wrote the report of vibrio in Delaware Bay. "Predictions on this season really rest on the sea surface temperature in the next coming months. We are having a heat wave now, with multiple days in the 90s, and if it continues during July, the water may warm up enough to support the growth of vibrio."

In Texas, there have been six confirmed cases of Vibrio vulnificus in 2019, says Lara Anton, a Department of State Health Services spokeswoman. None were fatal.

In Florida, officials confirmed 42 cases of Vibrio vulnificus in 2018, and 9 of those patients died. “We have had 8 cases of Vibrio vulnificus in 2019, none of them fatal," says Emerson George, a spokesperson for the Florida Department of Health. Reports of two vibrio cases this year in Florida, one fatal, have not been confirmed.

Public health officials warn that people with cuts, scrapes, and certain health conditions should stay out of warm saltwater and not eat raw or undercooked seafood to avoid the infection.

Taking simple steps to lessen your risk and understanding the disease's symptoms can lower the chances that you'll get a serious infection. We turned to infectious disease experts and the CDC to find out more about the bacteria.

Why is vibriosis sometimes linked to 'flesh-eating bacteria' disease?

If vibriosis causes a skin infection and becomes severe, it can progress to a ''flesh-eating bacteria'' infection, also called necrotizing fasciitis. It's a serious infection of the connective tissues that surround muscles, nerves, fat, and blood vessels, and it can spread quickly, the CDC says.

While vibrio bacteria can cause necrotizing fasciitis, other types, especially streptococcus (group A strep) are the more common causes, the CDC says. Klebsiella, clostridium, E. coli, Staphylococcus aureus, and Aeromonas hydrophila can also lead to necrotizing fasciitis.

How does infection happen?

For the skin infection caused by vibrio, "The key here is you have an opening in your skin that allows the bacteria to get into it," says Jason Newland, MD, a professor at Washington University in St. Louis.

Bacteria can enter through cuts, scrapes, burns, insect bites, or puncture wounds, the CDC says.

What are the symptoms of a Vibrio infection?

If the bacteria enter the body through a cut or wound, a skin infection can happen and can become severe quickly.

When the bacteria are swallowed, symptoms can include watery diarrhea, nausea and vomiting, fever, chills, and stomach cramps, usually within 24 hours of eating the food. These symptoms can last about 3 days, the CDC says, or can be more severe and become life-threatening.

How often does vibriosis happen, and how often is it fatal?

The CDC says about 80,000 people become sick with vibriosis each year and 100 people die from it every year. Many people with Vibrio vulnificus infections require intensive care or limb amputations, and about 1 in 5 people with this infection die, sometimes within a day or two of becoming ill.

Can you avoid vibriosis?

Good hygiene can lessen the chance of getting a skin infection, says Aaron Glatt, MD, spokesperson for the Infectious Diseases Society of America. If you get a cut or other wound, taking care of it is crucial. Wash it with soap and water, and watch it to be sure it heals well.

Anyone with an open cut should stay out of warm saltwater, where the bacteria thrive. 

Don't eat raw or undercooked seafood, especially oysters, to avoid diarrhea, public health officials caution.

How is vibriosis diagnosed and treated?

A doctor may suspect vibriosis when you have watery diarrhea after eating raw or undercooked seafood or after you get a skin infection after being in seawater, the CDC says.

Tests of your blood, stool, or the wound can confirm the diagnosis.

If your stomach infection is mild, drinking plenty of fluids can help replace what was lost from diarrhea, the CDC says. Antibiotics may or may not fight vibriosis depending on which species of vibrio caused the infection.

If your stomach symptoms become worse or if the skin infection does not improve, you will need emergency medical help. For severe infections, you may need to be in the intensive care unit. If the skin infection becomes necrotizing fasciitis, the affected skin may need to be cut away; in severe cases, you may need an amputation.

Show Sources

CDC: "Vibrio Species Causing Vibriosis."

Jason Newland, MD, professor, Washington University in St. Louis.

Aaron Glatt, MD, hospital epidemiologist and chair of the department of medicine, South Nassau Communities Hospital; Infectious Diseases Society of America spokesperson; clinical professor of medicine, Icahn School of Medicine at Mount Sinai.

Katherine Doktor, MD, assistant professor of infectious diseases, Cooper Medical School at Rowan University, Camden, N.J.

Lara Anton, spokesperson, Texas Department of State Health Services.

Annals of Internal Medicine, June 18, 2019.

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