The Centre for Health Protection has received five reports of suspected shellfish poisoning affecting five men and eight women aged 11 to 57.

The patients developed nervous system-related symptoms including dizziness, limb weakness, blurred vision and cramps after eating steamed scallops at home on March 14 and 15.

The scallops were bought from markets in Tin Shui Wai, Yuen Long and North, Eastern and Wong Tai Sin Districts.

The cases, the first reported in 2005, have been referred to the Food & Environmental Hygiene Department for follow-up action.

The department has received 11 reports of shellfish poisoning in the last five years.

Shellfish safety

Poisoning can result from ingestion of shellfish contaminated with a toxin called phycotoxins. These are produced by free-living micro-algae, upon which the shellfish feed.

Bivalve shellfish like scallops, clams, mussels, oysters, and fan shells, which are filter-feeders and naturally ingest the toxic algae in water, are common vehicles responsible for shellfish poisoning.

When consuming shellfish, buy from reputable and licensed seafood shops. Eat only a small amount in any one meal, and avoid eating the viscera and roe.

Thorough cooking

Although toxins cannot be destroyed through cooking, boiling temperatures can highly reduce the risk.

Children, the elderly and ill, who are more susceptible to poisoning, should be cautious when consuming shellfish.