Vibrio parahaemolyticus

Transmission occurs mainly via the consumption of raw, undercooked, or contaminated shellfish, particularly oysters. A higher risk of transmission has been linked to the warmer months of the year when the bacteria, which reside in marine silt during the cooler months, live freely in the water and within fish and seafood. Person-to-person transmission is rare and is fecal-oral in nature.

The bacteria are also capable of causing wound infections, which can occur either through the exposure of a new wound caused by an immediate injury or pre-existing wound to brackish, estuarine or marine waters. An infection can also occur if the wound is exposed to raw fish or shellfish, or their drippings.

Illness onset can occur between 4 to 96 hours after exposure. The intestinal presentation of the illness is typically moderate in severity and resolves within 1-7 days.

Symptoms include:

• Watery diarrhea
• Nausea and vomiting
• Abdominal cramps
• Fever and headache

Severe symptoms occur in a quarter of those affected and include:

• Dysentery-like illness
• Bloody or mucoid diarrhea
• High fever
• Elevated white blood cell count
• Rarely- Systemic infection and death

Severe illness is more common in individuals with weakened immune systems.

Wound infections have the following symptoms:

• Rapid development of severe infection of affected wound
• Localized swelling
• Anemia from red blood cell destruction
• Low blood pressure

General recommendations for avoiding Vibrio parahaemolyticus gastrointestinal illness:

• Implement refrigeration of seafood from harvesting/purchase to consumption.
• Avoid the consumption of raw seafood, especially oysters, if:
  • They have come from coastal waters during the warmer months of the year
  • You have a weakened immune system
• When preparing oysters, mussels or other molluscan shellfish-
  • Before cooking, discard any opened shells
  • Boil, broil or fry (at 375 F) for at least 3-5 minutes
  • Bake at 450 F for 10 minutes
  • As a rule - discard any unopened shells after cooking
• Only eat shellfish or shellfish that is thoroughly cooked until steaming hot.
• Eat shellfish immediately after cooking and refrigerate leftovers.
• Avoid cross contaminating raw juices from seafood with other foods, and immediately cleanup any spills with hot water and soap and clean rising water.
• Keep raw seafood separate from other food.
• Thoroughly wash hands, utensils and surfaces after preparing or handling raw seafood.

General recommendations for avoiding wound infections:

• Do not handle raw seafood of any kind if you have a pre-existing wound.
• Wear protective clothing (e.g. Gloves) when handling raw seafood.
• Avoid marine, estuarine or brackish water if you have a pre-existing wound.
• If you sustain a wound or injury while exposed to salty seawater or while handling seafood, thoroughly clean and disinfect the area immediately and seek medical attention if the area becomes inflamed.

Over the last five years, 2015-2019, the average number of Vibrio parahaemolyticus infections reported in Texas has been 31 cases per year (ranging from 22 to 43). Infections also appear to be seasonal in nature, with most (67% in 2019) occurring between May and October.

There is no vaccine for Vibrio parahaemolyticus.

Report Vibrio infection, including cholera within one working day to (800) 705-8868 or (800) 252-8239.

Bad Bug Book (PDF) 2012  
U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition
Name of the Organism; Nature; Diagnosis of Human Illness; Associated Foods; Relative Frequency of Disease; Course of Disease and Complications...

Vibrio parahaemolyticus
Centers for Disease Control and Prevention
General Information, Technical Information, Additional Information...

Vibrio parahaemolyticus is a bacterium commonly found in coastal marine waters and seafoods throughout the world.

This bacteria can make people sick in two ways. If it 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.

The bacteria can also 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 from 1-7 days, and usually begins within 12 and 24 hours of eating contaminated seafood, but can range from 4 to 30 hours.

In the United States, diarrheal illness is due to either eating raw and other improperly cooked shellfish or by consuming cooked fish and 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 properly chilled, the bacteria will grow rapidly in the seafood which then can make people sick.

In some cases, seafood can naturally become highly contaminated with these bacteria while it is still in coastal waters before being harvested.

Vibrio parahaemolyticus infections are fairly rare, but they are also under-reported to public health officials. In Texas, we usually have between 2 and 7 cases reported each year. Between 1988 and 1997, a total of 42 individuals were reported with a Vibrio parahaemolyticus infection in Texas. In most years, the majority of reported cases are of people with a skin or wound infection. In 1998, however, most of the people with this illness had diarrhea from eating raw seafood.

The diagnosis of this illness is made by taking stool samples from a sick person. The stool sample is allowed to grow more bacteria, then it is studied in a laboratory. The Texas Department of State Health Services is asking physicians to send stool samples from people who may have this illness to a laboratory. Laboratories must perform a special test on the stool sample to see if the sickness was caused by this bacteria. The Health Department has told doctors to suspect this illness when patients complain of diarrhea with fever, if the patient has eaten raw seafood.

Most people can 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.

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

Only raw seafood can cause this illness, so:

1. Cook shellfish (oysters, clams, mussels) thoroughly.
2. For shellfish in the shell either:
   • boil until the shells open and continue boiling for five more minutes, or
   • steam until the shells open and continue cooking for nine minutes;
   • For shucked oysters, boil for at least three minutes or fry them in oil at least 10 minutes at 350 degrees.
3. Do not eat shellfish that do not open during cooking.
4. Do not allow seafood already cooked to touch raw seafood, and do not touch cooked seafood after you have handled raw seafood without washing your hands first. 

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)