Vibrio Infections

Vibrio is a gram-negative rod that naturally lives in coastal waters, including salt water and brackish water. They cause an estimated 80,000 illnesses in the US each year. About a dozen species of Vibrio are pathogenic to humans. Vibrio parahaemolyticus causes the most infections in the United States, accounting for about 40% of reported cases of vibriosis, followed by Vibrio alginolyticus, which accounts for about 20%. Most people infected with these Vibrio species develop diarrhea. Some might also experience stomach cramping, nausea, vomiting, fever, and chills. 

V. vulnificus is most often associated with life-threatening soft-tissue infections. As a result, it is commonly referred to as “flesh-eating bacteria.” V. vulnificus infections can rapidly progress from an initial presentation of cellulitis, tenosynovitis, or necrotizing fasciitis to septicemia and death within 48 to 72 hours. Most cases occur from June to September, which is the optimal time for bacterial growth in warm coastal water and increased human water-related activities. 

Most people become infected with Vibrio species by eating raw or undercooked shellfish, particularly oysters. Some people get infected when an open wound is exposed to salt water or brackish water containing Vibrio. People can also get infected if an open wound comes in contact with raw or undercooked seafood. Open wounds include those from recent surgery, piercing, tattoo, and other cuts or scrapes. People at higher risk for wound infection include those with underlying health conditions such as liver disease, diabetes, and immunosuppression.

Hurricane Ian was associated with 74 cases of V. vulnificus wound infections and 17 deaths in 2022. CDC issued a health alert in 2023 regarding severe V. vulnificus infections in the US associated with warming coastal waters. That year, the US experienced above-average coastal sea surface temperatures, widespread heat waves, and severe storms with flooding. These are exactly the conditions in which V. vulnificus thrives. Hurricane Helene caused a spike of 82 cases and 19 deaths in 2024. The Florida Department of Health reported 11 cases and 4 deaths from V. vulnificus during the first half of 2025.  

Signs and symptoms of vibrio sepsis and necrotizing fasciitis include fevers and chills, localized severe swelling, rapidly developing cellulitis, purpura, and hemorrhagic bullae. According to CDC epidemiological surveillance data, the mortality rate is 50% among patients presenting with V. vulnificus septicemia and 15% among those with a wound infection without septicemia. Patients who survive often require amputation of the affected limb.

Vibrio organisms can be isolated from the stool of patients with gastroenteritis, from blood specimens, and from wound exudates. Fecal specimens are inoculated onto thiosfulfate-citrate-bile salts-sucrose agar, which inhibits the growth of normal bowel flora. Suspect colonies can be rapidly identified by MALDI-TOF spectrometry. Because identification of the organism in stool requires special techniques, laboratory personnel should be notified when infection with Vibrio species is suspected.

Clinical laboratories should submit all known or suspected Vibrio isolates to the local, state, territorial, or tribal public health laboratory. Local, state, territorial, and tribal public health laboratories should perform whole genome sequencing if possible and submit the results to PulseNet. 

References

CDC Health Alert Network, Severe Vibrio vulnificus infections in the US associated with warming coastal waters, September 1, 2023, CDCHAN-00497.

Archer EJ et al. Climate warming and increasing Vibrio vulnificus infections in North America, Sci Rep. 2023;13(1):3893.