What are Vibrio bacteria?

Vibrio bacteria naturally live in certain coastal waters and are present in higher concentrations between May and October when water temperatures are warmer.

What is vibriosis?

About a dozen Vibrio species can cause human illness, known as vibriosis. The most common species causing human illness in the United States are Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio alginolyticus.

How do people get vibriosis?

Most people become infected by eating raw or undercooked shellfish, particularly oysters. Certain Vibrio species can also cause a skin infection when an open wound is exposed to salt water or brackish water. Brackish water is a mixture of fresh and salt water. It is often found where rivers meet the sea.

Who is more likely to get vibriosis?

People with compromised immune systems, especially those with chronic liver disease, are more likely to get vibriosis. Eating raw seafood, particularly oysters, and exposing open wounds to salt water or brackish water can increase a person’s chance for getting vibriosis.

During which months are people more likely to get vibriosis?

About 80% of infections occur between May and October when water temperatures are warmer.

How common is vibriosis?

CDC estimates that vibriosis causes 80,000 illnesses each year in the United States. About 52,000 of these illnesses are estimated to be the result of eating contaminated food.

The most commonly reported species, Vibrio parahaemolyticus, is estimated to cause 45,000 illnesses each year in the United States.

Is vibriosis a serious disease?

Most people with a mild case of vibriosis recover after about 3 days with no lasting effects. However, people with a Vibrio vulnificus infection can get seriously ill and need intensive care or limb amputation. About 1 in 5 people with this type of infection die, sometimes within a day or two of becoming ill.

How can vibriosis be prevented?

To reduce your chance of getting vibriosis, don’t eat raw or undercooked shellfish, such as oysters. If you have a wound (including cuts and scrapes), avoid contact with salt water or brackish water or cover the wound with a waterproof bandage if there’s a possibility it could come into contact with salt water or brackish water, raw seafood, or raw seafood juices.

When ingested, Vibrio bacteria can cause watery diarrhea, often accompanied by abdominal cramping, nausea, vomiting, fever, and chills. Usually these symptoms occur within 24 hours of ingestion and last about 3 days. Severe illness is rare and typically occurs in people with a weakened immune system.

Vibrio bacteria can also cause a skin infection when an open wound is exposed to salt water or brackish water. Brackish water is a mixture of fresh and salt water. It is often found where rivers meet the sea.

CDC estimates 80,000 people become sick with vibriosis, and 100 people die from their infection, in the United States every year.

Could You Get Sick?

Anyone can get sick from vibriosis, but you may be more likely to get an infection or severe complications if you:

• Have liver disease, cancer, diabetes, HIV, or thalassemia
• Receive immune-suppressing therapy for the treatment of disease
• Take medicine to decrease stomach acid levels
• Have had recent stomach surgery

Don’t chance it! Some Vibrio species, such as Vibrio vulnificus, can cause particularly severe and life-threatening infections. Many people with V. vulnificus infections require intensive care or limb amputations, and about 1 in 5 people with this infection die, sometimes within a day or two of becoming ill.

Diagnosis

A clinician may suspect vibriosis if a patient has watery diarrhea and has recently eaten raw or undercooked seafood, especially oysters, or when a wound infection occurs after exposure to seawater. Infection is diagnosed when Vibrio bacteria are found in the stool, wound, or blood of a patient who has symptoms of vibriosis.

Treatment

Treatment is not necessary in mild cases, but patients should drink plenty of liquids to replace fluids lost through diarrhea. Although there is no evidence that antibiotics decrease the severity or duration of illness, they are sometimes used in severe or prolonged illnesses.

Reduce your risk of vibriosis by following these tips:

• Don’t eat raw or undercooked oysters or other shellfish. Cook them before eating.
• Always wash your hands with soap and water after handing raw shellfish.
• Avoid contaminating cooked shellfish with raw shellfish and its juices.
• Stay out of salt water or brackish water if you have a wound (including cuts and scrapes), or cover your wound with a waterproof bandage if there’s a possibility it could come into contact with salt water or brackish water, raw seafood, or raw seafood juices. Brackish water is a mixture of fresh and salt water. It is often found where rivers meet the sea.
• Wash wounds and cuts thoroughly with soap and water if they have been exposed to seawater or raw seafood or its juices.
• If you develop a skin infection, tell your medical provider if your skin has come into contact with salt water or brackish water, raw seafood, or raw seafood juices.

If you are in a group more likely to get vibriosis:

• Wear clothes and shoes that can protect you from cuts and scrapes when in salt water or brackish water.
• Wear protective gloves when handling raw seafood.

Vibrio and Oysters

Many people enjoy eating raw oysters, and raw oyster bars are popping up at some of the trendiest restaurants. But eating raw oysters and other undercooked seafood can put you at risk for infections, including vibriosis, which is caused by certain strains of Vibrio bacteria.

Vibrio bacteria naturally inhabit coastal waters where oysters live. Because oysters feed by filtering water, bacteria can concentrate in their tissues. When someone eats raw or undercooked oysters, viruses or bacteria that may be in the oyster can cause illness.

You can get very sick from eating raw oysters.

Most Vibrio infections from oysters result in only diarrhea and vomiting. However, some infections, such as those caused by Vibrio vulnificus, can cause more severe illness, including bloodstream infections and severe blistering skin lesions. Many people with V. vulnificus infections require intensive care or limb amputations, and 15-30% of infections are fatal.

It is impossible to tell that an oyster is bad by looking at it.

An oyster that contains harmful bacteriadoesn’t look, smell, or even taste different from any other oyster.

You can get sick from eating oysters during any month of the year.

While most vibriosis cases occur during warmer months of the year, cases have been reported year-round.

The only way to kill harmful bacteria in oysters is to cook them properly.

Hot sauce and lemon juice don’t kill Vibrio bacteria. Drinking alcohol while eating oysters doesn’t kill Vibrio bacteria either. Cooking oysters properly kills harmful bacteria.

Tips for Cooking Shellfish

Before cooking, discard any shellfish with open shells.

For shellfish in the shell, either:

• Boil until the shells open and continue boiling another 3-5 minutes, or
• Add to a steamer when water is already steaming, and cook for another 4-9 minutes.

Only eat shellfish that open during cooking. Throw out any shellfish that do not open fully after cooking.

For shucked oysters, either:

• Boil for at least 3 minutes,
• Fry in oil for at least 3 minutes at 375° Fahrenheit,
• Broil 3 inches from heat for 3 minutes, or
• Bake at 450° Fahrenheit for 10 minutes.

Raw oysters can ruin your summer. That’s because you can get very sick from eating raw oysters. Learn about vibriosis—a disease linked to raw oysters—and how to protect your health when it comes to oysters and certain other shellfish.

Most illnesses from raw oysters occur in summer. Whenever and wherever you like to enjoy oysters, eating raw oysters and certain other undercooked shellfish, such as clams and mussels, can put you at risk for infections.

Oysters eat by constantly drawing in water and materials in the water, including harmful bacteria and viruses. These bacteria and viruses can become concentrated in an oyster’s body and infect people who eat the oysters raw or undercooked. One of the infections people get from eating raw oysters is caused by some types of Vibrio—bacteria that occur naturally in coastal waters where oysters grow. This infection is called vibrioisis. People also can get vibriosis after exposing a wound to salt water or brackish water containing the bacteria. Brackish water is a mixture of fresh and salt water. It is often found where rivers meet the sea.

About 80,000 people get vibriosis—and 100 people die from it—in the United States every year. Most of these illnesses happen from May through October when water temperatures are warmer. However, you can get sick from eating raw or undercooked oysters during any month of the year, and raw oysters from typically colder waters also can cause vibriosis.

An oyster that contains harmful bacteria doesn’t look, smell, or even taste different from any other oyster. The only way to kill harmful bacteria in oysters is to cook them properly.

What are the symptoms of vibriosis?

Most Vibrio infections from oysters, such as Vibrio parahaemolyticus infection, result in mild illness, including diarrhea and vomiting. However, people with a Vibrio vulnificus infection can get very sick. As many as 1 in 5 people with a V. vulnificus infection die. This is because it can lead to bloodstream infections, severe blistering skin lesions, and limb amputations. If you develop symptoms of vibriosis, tell your medical provider if you recently ate or touched raw shellfish or came into contact with brackish or salt water.

Who is more likely to get vibriosis?

Anyone can get sick from vibriosis, but you may be more likely to get an infection or severe complications if you:

• Have liver disease, alcoholism, cancer, diabetes, HIV, or the blood disorder thalassemia.
• Receive immune-suppressing therapy for the treatment of disease, such as cancer.
• Have an iron overload disease, such as hemochromatosis.
• Take medicine to lower stomach acid levels, such as Nexium and Pepcid.
• Have had recent stomach surgery.

How do people get vibriosis?

Most people become infected by eating raw or undercooked shellfish, particularly oysters. Other people become infected by:

• Getting brackish or salt water in a wound, such as when they’re swimming, wading, or fishing.
• Cutting themselves on an item, such as a rock or pier, that has come into contact with brackish or salt water.
• Getting raw seafood juices or drippings in a wound.

How can I stay safe?

Follow these tips to reduce your chances of getting an infection when eating or touching shellfish and other seafood:

• Don’t eat raw or undercooked oysters or other shellfish. Fully cook them before eating, and only order fully cooked oysters at restaurants. Hot sauce and lemon juice don’t kill Vibrio bacteria and neither does alcohol.
  • Some oysters are treated for safety after they are harvested. This treatment can reduce levels of vibriosis in the oyster, but it does not remove all harmful germs. People who are more likely to get vibriosis should not eat any raw or undercooked oysters.
• Separate cooked seafood from raw seafood and its juices to avoid cross contamination.
• Wash your hands with soap and water after handling raw seafood.
• Cover any wounds if they could touch raw seafood or raw seafood juices or come into contact with brackish or salt water.
• Wash open wounds and cuts thoroughly with soap and water if they have been exposed to seawater or raw seafood or its juices.

Vibrio cholerae is a species of Vibrio bacteria. Some types of Vibrio cholerae bacteria cause serious diarrheal illness called cholera, and others cause illness that’s typically less serious. This page describes infections involving Vibrio cholerae that do not cause cholera.

Questions and Answers

What’s the difference between Vibrio cholerae that cause cholera and those that don’t?

Two serogroups (O1 and O139) or types of Vibrio cholerae bacteria can produce cholera toxin that causes the disease we call cholera. About 1 in 10 people infected with cholera toxin-producing O1 or O139 Vibrio cholerae experience severe, life-threatening illness, and both serogroups can cause widespread epidemics. Learn about this severe, life-threatening illness and the serogroups that cause it.

All other Vibrio cholerae types are known as “non-cholera Vibrio cholerae.” These include strains of Vibrio cholerae O1 and O139 that do not produce cholera toxin. Most illnesses these bacteria cause are mild, and these bacteria do not cause epidemics.

How do people become infected?

Like Vibrio species that cause vibriosis, non-cholera Vibrio cholerae bacteria naturally live in coastal waters and are present in higher concentrations when water temperatures are warmer. Most infections occur during warm weather.

In the United States, most people become infected by eating raw or undercooked shellfish, particularly oysters. The bacteria also can cause an infection when an open wound is exposed to salt water or brackish water, which is a mixture of fresh and salt water that’s often found where rivers meet the sea. Learn about other Vibrio species that can cause diarrheal illness and wound infection.

Casual contact with an infected person does not put someone at risk of infection.

What are the symptoms of infection?

• Most people experience diarrhea, which can range from mild to severe and watery.
• Some people experience fever.
• People with a wound infection may experience redness and swelling at the infection site.

How is infection diagnosed?

A doctor may suspect Vibrio infection if a patient has diarrhea and has recently eaten raw or undercooked seafood, especially oysters, or when a wound infection has developed after a wound was in contact with salt water or brackish water.

Infection is diagnosed when Vibriocholerae bacteria that do not produce cholera toxin are found in a sample of the stool, in a wound, or in the blood of the patient.

How is infection treated?

People with diarrhea should drink plenty of liquids to replace lost fluids.

Most people with non-cholera Vibrio cholerae infection recover without antibiotic treatment within a few days. However, antibiotics are sometimes used to treat people with these Vibrio infections, including people with severe or prolonged illness, those at risk of severe illness, and those with a wound infection.

Who is more likely to get an infection or severe illness?

Anyone can become infected, but those at increased risk of infection or severe illness include those who:

• Have liver disease, cancer, diabetes, HIV, or thalassemia (an inherited blood disorder)
• Receive immune-suppressing therapy for the treatment of disease
• Take medicine to decrease stomach acid levels
• Have had stomach surgery

How can infection be prevented?

The following tips can help reduce your chance of infection:

• Do not eat raw or undercooked shellfish, such as oysters.
• If you have a wound, you should avoid contact with salt water, brackish water or seafood juices from wading, fishing, or cleaning seafood. If you cannot avoid these potential exposures, cover your wound with a waterproof bandage.
• You should wash wounds with soap and water as soon as possible if they are exposed to salt water, brackish water, raw seafood, or raw seafood juices.

How common is infection?

Non-cholera Vibrio cholerae are the third most commonly reported group of Vibrio bacteria causing infection in the United States, with about 100 cases reported each year. Many more cases, however, are likely not diagnosed or reported.