Vibrio is a genus of bacteria that includes several species that are important causes of human disease. The most infamous of these diseases is caused by Vibrio cholerae, which causes cholera. Other significant species causing illness in humans are Vibrio vulnificus and Vibrio parahaemolyticus. Globally, these infections sicken many people and are sometimes fatal.
Vibrio infections of all types have some significant things in common. They all occur in salty or brackish waters, mostly seawater but also in inland bodies of water that have a higher salt content, including some lakes and ponds, especially those that may be near bodies of salt water where intrusion can occur. Infection most commonly results when people drink water contaminated with the feces of an infected person but people can also be sickened from eating seafood, especially shellfish, most commonly oysters, that have grown in contaminated water and which are eaten raw or undercooked. It is important to note that while oysters are a common culprit in infections that occur in the United States, other shellfish species can also carry the infection. In addition, people who suffer injuries to the skin either while in infected water, or people who have open wounds that come in contact with infected water, may also become infected with Vibrio.
In those parts of the world where Vibrio infections are relatively common (Africa, Indian subcontinent, Haiti, and parts of Southeast Asia) infected water sources are the most common culprit and sometimes visitors to these areas may become infected as well. Sometimes the infection occurs in epidemic outbreaks but these are usually well advertised through the news media so it is unlikely a traveler would encounter one of these situations unaware and even if they did, travelers only rarely become infected even during an outbreak. When traveling, especially in Vibrio endemic areas, it is critical that only sealed bottled water be consumed or used for brushing teeth etc. Always be sure food is cooked thoroughly, especially seafood, and avoid raw or unpeeled fruits and vegetables.
Vibrio in the United States
While cholera is relatively rare in the United States and almost always occurs in people who have traveled to infected areas, it used to be common in the United States before the widespread treatment of drinking water, especially in coastal areas. It can still occur, however, so caution is warranted, especially with raw or undercooked shellfish. More likely, people in the United States will be infected with V. vulnificus from undercooked shellfish, including oysters or crayfish, especially those harvested in the Gulf of Mexico, or through traumatic injury in seawater. This infection can be highly fatal or disfiguring to those with compromised immune systems or in those who have extensive liver damage, especially damage due to alcoholism. Even more common in the United States is infection with V. parahaemolyticus, again either through the ingestion of contaminated raw or undercooked shellfish or through traumatic injury in seawater. V. parahaemolyticus annually infects over 4,000 people in the United States and that is highly likely to be an undercount since reporting is not consistent and many infected persons do not know they were infected since symptoms generally resolve on their own, except in immune compromised persons, in about three days.
Person-to-person transmission has never been highly implicated in Vibrio infections. Contact with infected environmental surfaces is also an unlikely route of infection, but as is known to happen with other food-borne illnesses, it is theoretically possible for infection to occur if contaminated foods directly or indirectly contact foods eaten fresh or raw through the use of contaminated cutting boards, countertops, utensils, or hands. Frequent and effective disinfection of kitchen items and surfaces can help reduce the risk of Vibrio, and other food-borne illness, transmission in the home or institution. Given the potential for serious illness, it pays to be cautious in the home kitchen, especially since so many common foods are sourced from around the world today, potentially including from infected areas.