The cleanup in the aftermath of Hurricane Milton, which swept through Florida this week leaving a trail of destruction and millions without power, has barely begun. But now, health experts are warning of a hidden threat that could be lurking in the floodwaters – a bacterium called Vibrio vulnificus.

There are around 12 Vibrio species that cause human disease, including Vibrio cholerae, the causative agent of cholera. Vibrio vulnificus is one of the rarest, but infections with this species are among the most serious. These bacteria are naturally found in coastal waters, especially during the warmer months of May to October.

Exposure to the bugs can lead to an infection called vibriosis, which brings with it a not-so-fun constellation of symptoms: vomiting and diarrhea, stomach cramps, and fever. If an open wound comes into contact with Vibrio-containing water, infection can result, causing pain, swelling, discoloration, and fever.

The majority of vibriosis cases arise from the consumption of raw or undercooked shellfish – Vibrio vulnificus is responsible for more than 95 percent of seafood-related deaths in the US. But spending time in water also poses a risk. Vibrio-infected wounds can quickly progress to a life-threatening situation, sometimes requiring surgery or even amputation, which is why experts are concerned about the floodwater that Hurricane Milton has left in its wake.

“Where you have salt water meeting fresh water, this is where Vibrio can thrive. And if individuals are exposed to brackish water and they have an open cut, or they’re immunocompromised, such as having cancer, Vibrio can take hold,” Dr Scott Rivkees, former Florida state surgeon general, told ABC News.

Debris strewn around by the storm can easily cause injuries, and bacterial infections are a risk even with tiny cuts and scrapes, so it’s vital to practice good hygiene if you do come into contact with any floodwater. The Centers for Disease Control and Prevention (CDC) recommends that any exposed skin be thoroughly cleaned with soap if possible, or with alcohol-based sanitizer. Clothes should also be put through a hot wash with detergent before wearing them again.

Ideally, it’s best to wait for the green light from public officials before re-entering a flooded area, but if exposure to floodwater is unavoidable the advice is to wear rubber boots, rubber gloves, and goggles. These precautions will help protect you not only from Vibrio, but from other nasties that can be found in contaminated water.

The Vibrio genus of bacteria may be considered “the most important group of bacterial pathogens found in marine and coastal waters,” according to the authors of a piece published in July in The Lancet Planetary Health. They explored how the risk these bacteria pose is increasing, thanks to a combination of greater seafood consumption, recreational use of coastal waters, and climate change.

The USA – and particularly the area around the Gulf of Mexico – has seen its fair share of Vibrio infections in recent decades. For Vibrio vulnificus specifically, as of October 4, 64 cases had been confirmed in the state of Florida in 2024.

As the long road to recovery begins for the areas most affected by Hurricane Milton, the Florida Department of Health has issued guidance on what signs to look for if you’re concerned about a possible Vibrio infection.

“Seek medical attention immediately if you experience symptoms associated with Vibrio vulnificus,” they say, “especially after exposure to floodwaters.”

The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.