Vibrio vulnificus Infection (including Necrotising Fasciitis caused by V. vulnificus)

Causative agent

Vibrio vulnificus (V. vulnificus) is a Gram-negative bacterium that is present naturally in warm marine environments, such as seawater and brackish water. Its concentration typically increases during the summer when seawater temperatures rise, leading to more recorded cases during the hotter months.

Clinical features

Wound infection with V. vulnificus may result in necrotising fasciitis (NF, commonly known as "flesh-eating infection"), which is a serious bacterial infection of the soft tissue and fascia (a sheet or band of fibrous connective tissue separating or binding muscles and organs together). Most patients present with signs of inflammation such as redness, swelling, and pain at the affected site. There may also be ulcers, blisters, or black spots. The patient may experience intense and severe pain which is out of proportion to the visible skin changes. Other symptoms can include fever, chills, fatigue, diarrhea, vomiting or pus from the infected area. NF can lead to rapid tissue destruction and potentially life-threatening complications. 

Consuming food that is contaminated with V. vulnificus may cause symptoms such as fever, chills, diarrhoea, vomiting, nausea and stomach cramps. In people with underlying medical conditions, in particular liver diseases, V. vulnificus can infect the bloodstream, typically causing fever, chills, decreased blood pressure and blistering skin lesions.

Mode of transmission

V. vulnificus infections are either foodborne or wound-associated. The infection is typically acquired from exposure to seawater through an existing open wound or puncture wound caused by handling raw seafood, or through eating raw or undercooked shellfish, particularly oysters, harvested from warm water. There is no evidence of human-to-human transmission.

High risk groups

All people are susceptible to V. vulnificus infection. People who frequently handle or have direct contact with raw seafood have a higher risk of acquiring V. vulnificus infection with NF. People with underlying medical conditions such as liver diseases, cancer, diabetes mellitus, thalassemia, impaired immune response or receiving immuno-suppressing therapy, may have an increased risk of getting infected or having severe complications. Besides, people who take medication to decrease stomach acid levels or who have had recent stomach surgery also have a higher risk of infection.

Incubation period

The incubation period is usually 12 to 72 hours.

Management

For mild V. vulnificus infections with diarrhoea or vomiting, replacement of fluids is usually sufficient. For those involving NF, prompt antibiotic therapy is crucial. Surgical interventions, such as removal of dead tissue or amputation of the affected limb, are often required to stop the infection from spreading. Some patients may require intensive care, and the case fatality rate of V. vulnificus infection-associated NF is about 20%.

Prevention

To prevent V. vulnificus infection, members of the public, in particular people with impaired immune response or with underlying medical illnesses, should observe the following:

Proper wound management

• Clean wounds immediately and cover properly with waterproof adhesive dressings until healed.
• Prompt first-aid care of even minor, non-infected wounds.
• Perform hand hygiene before and after touching wounds.
• Avoid having wounds coming into contact with seawater or raw seafood.
• Consult doctor promptly if symptoms of infection develop, such as increasing redness, swelling and pain on the skin.

Proper food handling

• Avoid skin contact with dirty water when visiting wet market.
• Be careful with sharp parts of seafood, such as fish fins, shrimp heads and crabs to prevent cuts.
• Wear protective clothing (e.g. gloves) and cover all wounds when handling raw seafood.
• Cook seafood thoroughly; for shellfish (e.g. oysters, clams, mussels), cook until the shells open. Avoid eating raw oysters or shellfish.
• Avoid mixing ready-to-eat food and raw seafood to prevent cross-contamination.