Vibriosis, the illness resulting from infection with the bacteria Vibrio, is responsible for an estimated 80,000 illness and about 100 deaths in the United States each year. The Vibrio bacteria are actually in the same family as the bacteria that cause Cholera.
Foodborne illnesses account for 52,000 of these Vibrio infections. The most commonly reported species of this bacterium is Vibrio parahaemolyticus, which is estimated to cause 45,000 illnesses each year in the United States.
Vibrio bacteria invade the body in two main ways: through eating raw or undercooked seafood; or when open wounds are exposed to seawater or brackish water. Most Vibrio infections happen when the waters are warmer in the months of May through October. The most common species causing human illness in the United States include: Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio alginolyticus. There are over 80 species of Vibrio bacteria.
What are the Symptoms of Vibrio Infections?
Symptoms of Vibrio infection vary depending on the mode of infection. Internal infection caused by eating raw or undercooked seafood produces illnesses ranging from mild illness with about 3 days of symptoms and no lasting affects to severe illness and even limb amputation. In cases of Vibrio vulnificus,1 in 4 afflicted people die, often within one to two days of becoming ill.
The seriousness of any infection depends on many factors, including how much bacteria is ingested and the person’s underlying health conditions.
Ingestion symptoms include watery diarrhea, fever, chills, stomach cramps, nausea, and vomiting. Symptoms usually begin within 24 hours of ingesting contaminated food and generally last about 3 days. If the infection causes a more serious gastrointestinal issue, hospitalization may be necessary
An infected wound may turn into a condition known as necrotizing fasciitis, more commonly referred to as “flesh-eating bacteria.” Necrotizing fasciitis literally means “causing death of tissues” and can be serious if infection involves tissues surrounding muscles, nerves, fat, and blood vessels. This form of infection can spread very quickly, destroying the tissue as it spreads and may even require amputation to contain the infection.
While the Vibriobacteria is one cause of necrotizing fasciitis, other bacteria are more common culprits of this affliction. Other bacteria such as streptococcus (group A strep), clostridium, E. coli, Staphylococcus aureus, and Aeromonas hydrophilia are also known causes of necrotizing fasciitis.
How Does Someone Become Infected with Vibrio?
Vibrio bacteria live and grow in bodies of water all over the world. The bacteria, however, are most likely to be found in warmer waters and environments. It is not common to find Vibrio in winter months, or in colder waters. Although uncommon, it is still possible.
Most forms of vibriosis are caused by someone eating raw or undercooked shellfish. Oysters are high on the list of usual suspects, as are clams and mussels. While people with compromised immune systems, especially with existing chronic liver disease, are more likely to become ill from consuming Vibrio, anyone can fall ill from the bacterial infection and cautions should be observed to prevent infection.
External infection is caused by wound exposure to brackish or salt water. Open wounds exposed to this hazard are prone to infection. Cuts exposed to raw seafood, particularly oysters, are also at risk. This type of infection is where the necrotizing fasciitis comes into play.
How Does a Doctor Diagnose a Vibrio Infection?
Diagnosis can be difficult, as vibriosis is typically not a commonly reported illness. This is because this bacterium is not covered in routine laboratory testing. Therefore, this illness often requires additional investigation to appropriately diagnose. Either the healthcare provider or the patient must consider this as a possible cause of illness. This means there needs to be a prompting to test for it. It often requires a patient to identify the additional risk factor of consuming raw or undercooked seafood for the clinician to consider ordering the test or for the clinician to link watery diarrhea to Vibrio. Unless an outbreak has occurred, this might not be the first diagnosis a physician concludes is the cause of a patient’s illness.
Diagnostic testing may include genetic identification of bacteria found in stool, wound, or the blood of a patient who has symptoms of vibriosis. Some cell culture tests are available for some strains of Vibrioand may be unavailable for others.
How are Vibrio Infections Treated?
Treatment for mild internal vibriosis often include treatment of the symptoms and replacing fluids lost with diarrhea. Unfortunately, there is no evidence that antibiotics have any impact on treatment of this illness, though they are sometimes prescribed for severe or prolonged illness.
In the case of necrotizing fasciitis, removal of affected tissues is often necessary to prevent spread. This could be a small procedure for a mild case, but could involve amputation of limbs for widespread infection.
Are Vibrio Infections on the Rise?
Maybe. With global warming and the rise in marine water temperatures, scientists are seeing an increased number of Vibrio positive tests.
Can Vibrio Infections be Prevented?
As with any bacterial infection, the best form of prevention is cleanliness and avoiding eating high-risk foods. A person’s best bet to avoid infection is to avoid contact with brackish or salt water if they have a wound, regardless of size. If someone must interact with this health risk, be sure to use a waterproof bandage for protection or even water shoes are a good idea. Showering after swimming and using hand sanitizer are also good forms of prevention of infection.
If someone happens to injure themselves while in warm saltwater, appropriate wound care is crucial to avoid infection. Wash with soap and water and monitor it regularly to ensure the wound heals well. If infection seems to be creeping in, seeking medical attention immediately and identifying the risk factor of potential Vibrioinfection is crucial to avoid long term complications.
It is also a good idea to heed warning labels and not consume raw or undercooked shellfish, especially oysters. Cooked shellfish is a good alternative.
What are Some Shellfish Cooking Tips?
Proper cooking techniques are the best way to avoid consuming contaminated shellfish. First, identify and discard any shellfish with open shells. One should only consume shellfish that open during cooking. If any remain closed after cooking, those too should be discarded.
Cooking in the Shell
When cooking shellfish in the shell, you can either boil or steam them.
- Boiling: boil until shells open and continue boiling for 5 more minutes.
- Steaming: steam until shells open and continue steaming for 9 more minutes.
When coking shucked oysters, you can boil, fry, broil, or bake them.
- Boiling: boil for at least 3 minutes
- Frying: fry in oil for at least 3 minutes with an oil temperature of 375 ºF
- Broiling: broil 3 inches from the heat for 3 minutes
- Baking: bake at 450 ºF for 10 minutes
Myths Surrounding Vibrio and Raw Oysters
- Vibrio Myth: Hot sauce and alcohol do not kill Vibrio bacteria, and therefore, make raw oysters safe to eat.
- Vibrio Myth: Avoiding oysters harvested from polluted areas also does not reduce the risk. Vibrio bacteria grow in both polluted and unpolluted areas.
- Vibrio Myth: Only a few oysters can cause illness. According to Roberta Hammond, Ph.D there was a death caused by Vibrio after someone only ate only three oysters.