Know the Signs of Vibrio Vulnificus, a Deadly 'Flesh Eating' Bacteria

Each summer, millions of Americans flock to the Gulf coast to enjoy the surf, sand and seafood. If you've ever done so, chances are you've swum right alongside Vibrio, a group of bacteria that naturally inhabits many coastal waters around the world.

Vibrio vulnificus is one such species that thrives in warm coastal waters. You might know it better by its unofficial name: flesh-eating bacteria.

The idea of "eating flesh" is enough to send chills down the spine of nearly anyone, but in reality, Vibrio needs a way into your body, either through an open wound or by ingesting it through uncooked, raw seafood. Luckily, infections of Vibrio vulnificus are rare, averaging only 150 to 200 cases per year in the U.S., but they can be fatal if not properly treated in time.

We spoke with Dr. Wesley Long, medical director of diagnostic microbiology at Houston Methodist, about what you should know about V. vulnificus, including common signs and symptoms, who's most at risk for severe illness and steps you can take to prevent infection in the first place.

What is Vibrio vulnificus?

V. vulnificus is but one of many species of Vibrio bacteria there are in the world. Only about a dozen species of Vibrio can make humans sick. In the U.S. the three most common species that can cause human illness are Vibrio vulnificus, Vibrio alginolyticus and Vibrio parahaemolyticus. Cholera is also caused by a type of Vibrio (V. cholerae) that can cause severe diarrhea but is less common in the U.S.

They're found throughout the world in many marine environments, including salt water and brackish water, which is a mix of fresh and salt water. V. vulnificus in particular thrives in warm water and is rarely present in cooler temperatures, which is why most infections occur during the summer and early fall. However, in certain places like Florida, where the water is warm most of the year, it can be present year-round.

Because sea critters like oysters, clams and mussels feed by filtering water, Vibrio can accumulate and concentrate within their tissues, which is why eating raw or undercooked versions of these can make you sick.

The CDC estimates that around 80,000 cases of Vibrio infections — or vibriosis, the term for the illness — occur each year in the U.S., but only 150 to 200 of those are from V. vulnificus. Unfortunately, 1 in 5 people who get sick from V. vulnificus die, sometimes within a day or two of becoming ill, says the CDC.

How do you get V. vulnificus?

You don't have to be at the beach to get V. vulnificus. In fact, eating raw oysters is the most common way people become infected with V. vulnificus, but anything consumed raw from the ocean could be a mode of transmission for the bacteria, says Dr. Long.

The other way people become infected by V. vulnificus is through contact of any open wound with salt water or brackish water. This not only includes swimming, but also preparing seafood or handling marine equipment like boats where the water comes into contact with a cut or scrape on your body.

What does 'flesh eating' really mean in terms of these bacteria?

According to Dr. Long, V. vulnificus is one of a few different types of bacteria that can cause necrotizing fasciitis, the technical term for what people often refer to as flesh-eating disease.

"Bacteria like V. vulnificus and group A Streptococcus, which we study here at Houston Methodist, produce molecules called virulence factors that help to break down cells and tissues in order to gain access to nutrients inside that support their growth, bypass the host's immune system and protect it from the host's immune response," says Dr. Long. "Often, these types of infections can spread quickly, causing massive tissue destruction."

In reality, there's a variety of bacteria that can cause these sorts of "flesh-eating manifestations," he says. The only surefire way to know if it's V. vulnificus or not is to conduct a bacterial culture test.

What counts as an open wound?

"An open wound is anything that breaks the skin barrier and gives access to the underlying tissues or the bloodstream," Dr. Long says. "Even if you have a small cut, like a deep paper cut, if it's bleeding, at least for a short amount of time, you have the potential to introduce bacteria into that cut."

These types of small cuts, he says, tend to scab over, which forms a new barrier and provides some protection while a wound heals even though it isn't as effective as intact skin. Whereas if there's a larger, deeper cut or scrape or other wound that breaks the skin, it's going to take more time for those to completely heal and protect the tissues underlying the skin, Dr. Long says.

Cuts and scrapes are pretty obvious examples of open wounds, but some might not be as clear-cut (pun intended). Some open wounds you might not have thought about are recent piercings, which can take weeks or months to fully heal; fresh tattoos; and even recently popped pimples, which creates a tear in the skin.

(Related: Should You Put Hydrogen Peroxide on a Cut or Scrape?)

Who is most at risk for vibriosis?

Anyone can get vibriosis, but people with certain medical conditions need to be more careful about getting in the water and eating raw seafood, says Dr. Long. Those include:

• Liver diseases, including cirrhosis and hepatitis
• Moderate to heavy alcohol use
• Certain hereditary diseases, including thalassemia, hemochromatosis (excess iron) and Wilson disease (excess copper)
• Immunocompromising conditions
• Diabetes
• Kidney failure

Men older than 40 years old also tend to have more severe infections, says Dr. Long, in part because they are more likely to fall in one of the above categories.

Additionally, anyone with an open wound that hasn't yet closed or fully healed should not get in the water, he says. If you have a wound that's been healing for a while or is closing, Dr. Long recommends asking your doctor it's safe for you to swim or what precautions you should take.

Common signs and symptoms of Vibrio infection

When it comes to treating vibriosis, time is of the essence. If you notice a wound after you went swimming at the beach, riding in a boat or any other marine activity, you'll want to watch out for symptoms ranging from fever, chills, redness, pain, swelling and warmth to others like blisters, ulcers, skin discoloration, discharge (leaking fluids) and low blood pressure.

Other common signs include:

• Watery diarrhea
• Stomach cramps
• Nausea
• Vomiting

"In the event you notice a wound after coming into contact with warm salt or brackish water, pay attention to any changes in the wound and how fast it's happening," says Dr. Long. "You're looking for any signs and symptoms that an infection might be spreading beneath the surface."

You'll want to seek immediate care or go to the emergency room if you notice any signs of a Vibrio vulnificus bloodstream or wound infection.

"A V. vulnificus infection could rapidly progress over the span of a few hours and can potentially result in limb loss or life-threatening complications," says Dr. Long. "It can go south very fast."

How to prevent Vibrio infections

• If you have a wound, even a small one, stay out of salt water or brackish water, if possible. This includes skimming your feet along the beach or dangling your toes off the pier. You might also want to cover your wound with a waterproof bandage or wrap for added protection.
• If you don't have a wound, consider wearing swim shoes to protect your feet and avoid potential cuts while you're in the water.
• In the event you get a wound while in contact with sea/ocean water, thoroughly wash and clean the wound with clean, running water and soap.
• Eat raw seafood at your own risk, especially during the summer and early fall months, and wash your hands with soap and water after handling any raw seafood, too. If you have a cut or wound, try not to handle raw seafood, if possible — even if you're gloved.