Vibriosis is an illness caused by Vibrio bacteria, which are a natural part of the environment in coastal waters, including salt water and brackish water where rivers meet the sea. While many species can cause illness, the most common in the United States are Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio alginolyticus. The bacteria are more abundant in warmer waters, with most infections occurring between May and October.
How Vibrio Infections are Contracted
The primary way people become infected with Vibrio is by consuming raw or undercooked seafood, especially shellfish. Oysters are a common source because as filter feeders, they can accumulate the bacteria in their tissues at concentrations up to 100 times higher than in the surrounding water. An oyster containing these harmful bacteria will not look, smell, or taste any different from a safe one.
A second major route of infection is through direct contact with contaminated water. If a person has an open wound, even a minor cut, scrape, or a recent tattoo, it can become an entry point for the bacteria when exposed to salt water or brackish water. Handling contaminated seafood or its juices can also introduce the bacteria into a wound.
Signs and Symptoms of Vibriosis
The symptoms of a Vibrio infection depend on how the bacteria entered the body. When ingested, the gastrointestinal illness involves watery diarrhea, abdominal cramping, nausea, vomiting, fever, and chills. These symptoms appear within 24 hours of consuming the contaminated food and can last for about three days.
For infections that begin in a wound, the symptoms are localized to the site of exposure. These can include pain, swelling, redness, warmth, discoloration, and fluid leaking from the wound. One of the most severe complications arises from the species Vibrio vulnificus, which can cause necrotizing fasciitis, a rapidly progressing infection that destroys the flesh around the wound. This condition is sometimes referred to as a “flesh-eating” infection.
Necrotizing fasciitis is a medical emergency characterized by intense pain that may seem disproportionate to the visible signs on the skin. The skin may become warm, red, and swollen, with the area of inflammation spreading quickly. Blisters, ulcers, or black spots on the skin can also develop. About one in five people with a V. vulnificus infection die, sometimes within only a day or two of becoming ill.
Groups at Higher Risk for Complications
While anyone can contract vibriosis, certain individuals are more likely to experience severe illness, especially people with chronic liver disease like cirrhosis or hepatitis. Individuals with liver disease who consume contaminated raw oysters are 80 times more likely to develop a V. vulnificus infection and 200 times more likely to die from it compared to healthy individuals.
Other conditions that increase susceptibility include hemochromatosis (excess iron), diabetes, cancer, HIV, or any disorder that weakens the immune system. People receiving immunosuppressive therapy or taking medications to reduce stomach acid are also at greater risk. For these groups, a Vibrio infection is more likely to invade the bloodstream, causing fever, chills, dangerously low blood pressure, and blistering skin lesions.
Treatment and Prevention Strategies
Preventing vibriosis primarily involves careful food handling and wound management. To avoid foodborne illness, thoroughly cook all shellfish, particularly oysters, to an internal temperature of 145°F for 15 seconds to kill the bacteria. It is also important to prevent cross-contamination by keeping raw seafood and its juices separate from cooked foods and washing hands and surfaces after handling raw shellfish.
To prevent wound infections, individuals with any open cuts, scrapes, or even recent piercings and tattoos should avoid direct contact with salt water and brackish water. If exposure is unavoidable, the wound should be covered with a waterproof bandage. Should a wound come into contact with potentially contaminated water or raw seafood juices, it should be washed thoroughly with soap and water immediately.
Treatment for vibriosis varies with the severity of the illness. Mild gastrointestinal cases are managed by drinking plenty of fluids to prevent dehydration, and antibiotics are not recommended. However, for severe or prolonged infections, and for all wound infections, antibiotics are prescribed. In cases of necrotizing fasciitis, aggressive treatment is necessary and may involve surgery to remove the dead tissue, and in some severe instances, limb amputation may be required to stop the spread of the infection.