A group of bacteria found in seawater that can cause food poisoning, mainly from raw or undercooked seafood such as oysters.
A group of bacteria found in seawater that can cause food poisoning, mainly from raw or undercooked seafood such as oysters. Vibrio is a group of bacteria that live naturally in coastal and estuarine seawater, especially in warmer months. Several species can cause human illness, with Vibrio parahaemolyticus being a common cause of seafood-related food poisoning and Vibrio vulnificus causing rarer but far more serious infections. Because these bacteria concentrate in filter-feeding shellfish, the main risk to people is eating raw or undercooked seafood, particularly oysters, along with other shellfish and, occasionally, exposure of wounds to seawater. The typical gut illness from Vibrio parahaemolyticus brings watery diarrhoea, stomach cramps, nausea, vomiting and sometimes fever, usually appearing within about 24 hours and lasting a few days. Vibrio vulnificus is much more dangerous, especially for people with liver disease or weakened immune systems, and can cause severe bloodstream infection. Warmer water temperatures increase Vibrio numbers, so risk tends to rise in summer and in warmer regions of Australia. For Australian food businesses the key controls are safe sourcing and temperature management of seafood. Oysters and other shellfish should be bought from approved, monitored harvest areas that operate under shellfish quality-assurance programs, and kept cold throughout the supply chain, because Vibrio multiplies quickly when seafood warms up. Thorough cooking destroys the bacteria, so cooked seafood is much safer than raw. Businesses serving raw oysters and sashimi should keep them chilled at 5 degrees or below, minimise the time they spend out of refrigeration, and avoid cross-contamination between raw seafood and ready-to-eat food. Advising vulnerable customers, such as those with liver disease or weakened immunity, that raw seafood carries higher risk is prudent. Maintaining the cold chain from harvest to plate is the most effective way to keep Vibrio numbers low. A restaurant receives fresh oysters but leaves them sitting in a tray at room temperature on a warm day before service. Vibrio bacteria already present in the oysters multiply in the warmth. Customers who eat the raw oysters that night develop diarrhoea and cramps within a day. Keeping the oysters chilled at 5 degrees or below from delivery through to serving would have kept the bacterial numbers safe.
Frequently asked questions
What foods carry Vibrio?
Raw and undercooked seafood, especially oysters and other shellfish, are the main sources because these filter feeders concentrate the bacteria from seawater. Risk is higher in warmer months when Vibrio numbers rise.
What are the symptoms?
The common seafood illness causes watery diarrhoea, cramps, nausea, vomiting and sometimes fever within about a day, lasting a few days. Vibrio vulnificus can cause severe bloodstream infection in vulnerable people.
Who is most at risk of serious illness?
People with liver disease, weakened immune systems or other chronic conditions are at much greater risk of severe Vibrio vulnificus infection and should avoid raw seafood. Most healthy people experience only a milder gut illness.
Does cooking destroy Vibrio?
Yes, thorough cooking kills Vibrio bacteria, so cooked seafood is much safer than raw. The risk is concentrated in raw or undercooked shellfish such as oysters eaten straight from the shell.
How can a business reduce the risk?
Buy shellfish from approved, monitored harvest areas, keep seafood cold at 5 degrees or below throughout the supply chain, cook thoroughly where possible, and avoid cross-contamination. Maintaining the cold chain is the main control.
