Vibrio are a kind of bacteria that naturally live in warm ocean water. There are about a dozen Vibrio species that can cause illness in people, which is called vibriosis. The most common species that cause human illness in the United States are Vibrio parahaemolyticus, Vibrio vulnificus and Vibrio alginolyticus. There are higher concentrations of the bacteria in ocean water during the warm months of May to October.
There is no evidence of person-to-person transmission of vibriosis. The two main ways people get sick with vibriosis are:
- eating raw shellfish, particularly oysters, that are contaminated with Vibrio
- being exposed to Vibrio bacteria through open wounds while swimming or playing in warm oceanwaters
Vibrio can cause sickness and, in very rare instances, death. Some healthy people who come in contact with Vibrio bacteria will get sick, but most will have mild symptoms and will recover after about three days with no lasting effects. Those with weakened immune systems, especially those with chronic liver disease, are the most vulnerable to more serious illness.
More details about the different types of Vibrio bacteria and national monitoring efforts are available at cdc.gov/vibrio.
Symptoms of vibriosis
Symptoms include nausea, vomiting, diarrhea, abdominal pain, fever or shock following the ingestion of raw seafood, especially oysters, or with a wound infection after exposure to seawater.
A health care professional will typically treat a patient with antibiotics and monitor their patient’s recovery. Treatment may vary depending upon the person’s likelihood of developing serious illness from vibriosis.
Eating raw or undercooked shellfish, particularly oysters, poses the greatest risk of contracting vibriosis. Vibrio bacteria don’t alter the appearance, taste or odor of oysters.
To help prevent vibriosis, DHEC recommends:
- Not eating raw oysters or other raw shellfish.
- All South Carolina restaurants that serve shellfish must include a consumer advisory in their menus stating the risk for foodborned illness when eating raw or undercooked shellfish. It is a person’s choice to consume raw or undercooked shellfish, whether at home or at a restaurant.
- Cooking shellfish (oysters, clams, mussels) thoroughly. For shellfish in the shell, either a) boil until the shells open and continue boiling for five more minutes, or b) steam until the shells open and then continue steaming for at least nine more minutes. Don’t eat shellfish that stay closed shut during cooking. Boil shucked oysters at least three minutes, or fry them in oil at least 10 minutes at 375°F.
- Avoiding cross-contamination of cooked seafood and other foods with raw seafood and juices from raw seafood.
- Eating shellfish promptly after cooking and refrigerating leftovers.
- Avoiding exposure of open wounds or broken skin to any kind of salt water, or to raw shellfish harvested from such waters.
- Wearing protective gloves when handling raw shellfish.
DHEC’s role in protecting people from vibriosis
DHEC helps protect South Carolinians from vibriosis by regulating how shellfish are harvested, stored, processed, handled and transported. The agency also investigates cases of vibriosis reported to it so that additional cases can be prevented.
DHEC’s Shellfish Sanitation Program
- The primary goal of the Shellfish Sanitation Program is to ensure shellfish (oysters, clams and mussels) and the areas from which they are harvested meet the health and environmental quality standards required by federal and/or state laws and regulations.
- People who cultivate and harvest shellfish in South Carolina waters must follow the guidelines in the National Shellfish Sanitation Program Model Ordinance published by the United States Food & Drug Administration (FDA). Additionally, South Carolina has a vibrio management plan that is updated each year and evaluated by the FDA.
- If a foodborne illness is reported to DHEC and the patient has a positive Vibrio test from a doctor, DHEC’s retail food program and shellfish program work together to follow up with each restaurant and shellfish dealer that handled the shellfish in question. We review the handling, storage and transportation of the shellfish to determine compliance with federal and state requirements. When necessary, the shellfish is recalled to help protect others from becoming sick.
Vibriosis Case Investigations
- In South Carolina, all health care providers are required to report certain diseases or conditions found in their patients, including vibriosis, to DHEC. DHEC’s epidemiologists investigate these cases and determine, among other things, whether there is a disease outbreak. In general, a vibriosis outbreak is defined as two or more cases of non-cholera vibriosis that are associated with a common exposure (place and time).
- If an outbreak occurs, DHEC takes steps to prevent the spread of the disease or condition, which could include, if appropriate, notifying the public and issuing a recall in coordination with the FDA of implicated shellfish if shellfish is the source of the spread of the disease.
Health risks associated with natural waterbodies
South Carolina lakes, rivers, streams and coast are great places to cool off, but there is always a potential risk when swimming in natural waterbodies. Natural waterbodies are not sterile environments like swimming pools and spas – the presence of harmful bacteria, viruses and other organisms that can cause illness is always a possibility.
DHEC always recommends people evaluate a waterbody before entering in it. If a waterbody looks discolored, has a foul odor, noticeable algal mats, or dead fish or other animals, it’s advisable to not enter the water or allow pets or animals near that water.
DHEC continues to share important information about water safety with South Carolinians through news releases, webpages, social media, newsletters and communications with local officials and environmental groups.