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Fact Sheet: Vibrio Infection

What is Vibrio parahaemolyticus?

Vibrio parahaemolyticus is a bacterium commonly found in coastal marine waters and seafoods throughout the world. Vibrio bacteria are found in higher concentrations during the summer months as water becomes warmer.

What type of illness does Vibrio parahaemolyticus cause?

Vibrio can make people sick in two ways.

The bacterium can cause diarrhea in people who eat contaminated seafood. When this happens, the person usually only gets mildly or moderately sick, although some people may become sick enough to be hospitalized. The patient may have symptoms such as diarrhea, abdominal cramps, nausea, vomiting, headache, fever, and chills. The illness lasts 1 to 7 days, and usually begins 12 to 24 hours after eating contaminated seafood, but can begin anywhere from 4 to 30 hours after exposure. Read more about the risk of eating contaminated raw oysters.

If the bacterium enters an opening in the skin, it can cause a serious skin infection. This usually happens when a person with a cut or abrasion swims or fishes in seawater containing a high number of these bacteria.

How do people get the diarrheal form of this illness?

Usually people who get diarrhea from this bacterium have eaten raw or improperly cooked shellfish, or they have eaten cooked fish or shellfish that was contaminated with the bacteria after it was cooked. Most outbreaks have happened because the seafood was allowed to touch other raw seafood, dirty surfaces or utensils, or the seafood was not kept cold enough. If seafood is not kept clean and chilled, the bacteria will multiply rapidly in the seafood and are then more likely to make people sick.

How common are infections with Vibrio parahaemolyticus?

Vibrio parahaemolyticus infections are uncommon in Oregon. Most cases occur during the summer months when the water is warmer. Most illness in Oregon has been acquired by eating raw or undercooked seafood.

How are Vibrio parahaemolyticus infections diagnosed?

This infection is diagnosed by taking a stool sample from a sick person and submitting it to a clinical lab for culture. Laboratories must perform a special test on the stool sample to see if the sickness was caused by this bacterium. Doctors should suspect this illness when patients complain of diarrhea with fever after eating raw seafood.

How are Vibrio parahaemolyticus infections treated?

Most people get over this illness without any kind of treatment. However, a few people may be sick enough to be hospitalized and may need extra fluids. Antibiotics are generally not needed.

Are there any long-term effects associated with Vibrio parahaemolyticus infections?

No. These are short illnesses, and once you recover you should not expect any long-term effects.

How can I keep from getting this illness?

  1. Cook shellfish (oysters, clams, mussels) thoroughly.
    1. For shellfish in the shell either:
      1. Boil until the shells open and continue boiling for another 3 to 5 minutes, or
      2. Steam until the shells open and continue cooking for 4 to 9 more minutes;
    2. For shucked oysters, boil for at least 3 minutes or fry them in oil at least 3 minutes at 375 degrees F.
  2. Do not eat shellfish that do not open during cooking.
  3. Do not allow seafood that is already cooked to touch raw seafood, and do not touch cooked seafood after you have handled raw seafood without washing your hands first.

Who should be especially careful?

Certain health conditions put you at risk for serious illness or death if you become sick from eating contaminated raw seafood. People with the following health conditions should not eat seafood that is uncooked: 

  • Liver disease, either from excessive alcohol intake, viral hepatitis or other causes,
  • Hemochromatosis, an iron disorder,
  • Diabetes,
  • Stomach problems, including previous stomach surgery and low stomach acid,
  • Cancer,
  • Immune disorders, including HIV infection,
  • Long-term steroid use (as for asthma and arthritis).

Adapted from: Texas Department of Health
Issued by: Oregon Health Authority
Revised: August, 2014

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