"However, some strains do cause illness in humans. Symptoms are predominantly stomach cramps and watery diarrhoea and sometimes nausea, vomiting and fever.

"Generally people who are sick recover without hospital treatment, however, in severe cases hospitalisation is required.

"Additional testing is being done to confirm the type of Vibrio parahaemolyticus that has caused this illness. It is possible that the strain of Vibrio parahaemolyticus is unusually aggressive which may mean that even low numbers could cause illness.

"Additional testing of mussels and the waters that they are being grown in is also underway to help us understand why this has happened."

Mussel warning

• Don't eat raw or undercooked mussels 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.

• If you are pregnant or have low immunity, avoid eating any raw shellfish.