On reading an article on blood clams in the New York Times I was at first intrigued as I had never heard of them, then I tried to find somewhere in London I could have them with no luck so then google came up trumps as to why this may be the case as they are super dangerous as reported by the Shanghai Daily Mail in 2006
"Blood clams, considered delicious by many people, are still banned in the city because they may contain the hepatitis A virus and transmit other diseases such as hepatitis E, typhoid and dysentery, the Shanghai health officials said yesterday.
On Tuesday, health officials raided a Ningbo cuisine restaurant on Changyang Road in Yangpu District after receiving tips and confiscated 6 kilograms of blood clams hurriedly stashed in a cupboard.
The Shanghai Food and Drug Administration reminds residents not to eat the clams. They are also known as blood ark clams, red clams or, in Japan, akagai, because of the reddish or pinkish color of the mollusc itself.
The clams can be safely cultivated and kept pure and are eaten as sushi in Japan. But in Shanghai they are not safe, officials said.
The city has banned the clams since 1988, when more than 310,000 people were infected with hepatitis A - the main cause was eating dirty blood clams.
"The city government never removed the ban and for the sake of their health, the public shouldn't consume blood clams," said Gu Zhenhua, director of SFDA's health supervision department.
"Local people like to quickly boil blood clams in hot water and eat them with sauce, but this cooking method can't kill the virus," he said, adding that authorities frequently conduct sweeps in wet markets and restaurants for illegal blood clam business.
However, some restaurants still offer the clams, hiding them in refrigerators until they are requested by customers."