Vibriosis is an intestinal illness caused by bacteria called Vibrio. Vibrio are found in fish and shellfish that live in saltwater and the areas where freshwater meets saltwater, called estuarine environments. Although there are many species, Vibrio parahaemolyticus is the most common in the northwest.
Where Vibrio Comes From
Vibrio bacteria are found naturally in marine coastal waters, usually in low numbers that do not cause problems. They multiply rapidly in warm conditions, so fish and shellfish are more likely to be exposed to higher numbers in the summer.
How People Get Vibriosis
Most cases of vibriosis occur from eating raw or undercooked fish or shellfish. However, even fully cooked food can be re-contaminated if it’s rinsed with seawater. Shellfish should be kept cold after they’re harvested, and failure to do so can contribute to the growth of bacteria. Poor food handling practices during preparation or improper refrigeration of prepared seafood can also lead to illness. See Food Safety Tips for more information on safe food handling practices.
How to Prevent Vibriosis
Vibrio bacteria are destroyed by cooking shellfish to an internal temperature of 145° F for 15 seconds.
Eat only well-cooked shellfish, especially during the summer. Do not consider shellfish to be fully cooked right when the shells open. They need to cook longer to reach 145° F.
When harvesting:
- Right before you leave to harvest shellfish, check for closures and advisories due to Vibrio, biotoxins, and pollution at our Shellfish Safety Map, by contacting your local health department, or by calling our biotoxin hotline at 1-800-562-5632.
- Harvest the shellfish as soon as possible with the receding tide.
- Don't harvest shellfish that have been exposed to the sun for more than one hour (less in really hot weather).
- Keep the shellfish cold after they're harvested.
- Do not store shellfish in stagnant water.
Get more shellfish safety tips.
Who is at Risk
Anyone who eats raw or partially cooked fish or shellfish can become ill. People with liver disease, cancer, diabetes, HIV-AIDS, thalassemia (a type of anemia), a weakened immune system, recent stomach surgery, or who are over 65 are especially at risk for infections and complications due to Vibrio.
People taking antacids are more likely to get sick. Stomach acids help destroy bacteria, so when stomach acids are reduced, Vibrio bacteria are more likely to pass through the stomach and into the intestine, where the illness occurs.
Symptoms of Vibriosis
Symptoms include diarrhea, abdominal cramps, nausea, vomiting, headache, fever, and chills. Most Vibrio infections are not severe, but some people (especially those at high risk) may be sick for a week or more and may require hospitalization.
Symptoms usually appear about 12 to 24 hours after consumption, but it can take as long as 4 days.
Treatment for Vibriosis
Mild or moderate infections usually don’t require treatment. Severe infections can be treated with antibiotics.
I You Think You Have Vibriosis
Contact a health care provider if diarrhea lasts longer than 3 days or the illness is severe.
Report shellfish-related illnesses by filling out the Foodborne Illness Complaint Form.
Other Marine Vibrio Organisms
Several other marine Vibrio species found in Washington can cause intestinal illness (from consuming raw or undercooked seafood) or wound infections (from skin contact with marine water or seafood). Symptoms from these infections are similar to those from V. parahaemolyticus infections.
A type of Vibrio called Vibrio vulnificus is associated with severe intestinal and wound infections. It can cause serious complications and death. People at high risk for other Vibrio infections (see “Who is at Risk” above) are more likely to become infected.
As of 2025, there have been no reports of V. vulnificus infection attributed to the consumption of Washington state shellfish or skin contact with Washington marine waters. The first locally acquired V. vulnificus infections reported in Washington residents occurred in 2016 and 2017. One case occurred each year, and both were associated with handling farmed tilapia fish purchased from live freshwater tanks.
Other Illnesses Associated with Shellfish
There are several types of biotoxins found in the Northwest that can cause severe illness, and in extreme cases, death. Norovirus is also a concern. Some people can have an allergic reaction to shellfish.
More Resources
Foodborne Illness Notification System - Report suspected foodborne illnesses.