Beijing authorities have urged all restaurants in the capital to stop selling raw or undercooked fresh-water animals due to concerns about parasitic diseases.
Customers have been cautioned against eating dishes including snails, slugs, fish, shrimp, crabs, frogs and snakes due to the possibility they may contain harmful parasites, according to the Beijing Municipal Food Safety Administration.
The warning follows a mass food poisoning case that saw at least 23 diners contract eosinophilic meningitis - an infection of tissues around the brain - after eating Amazonian snails at two Sichuan restaurants.
Inspectors later found small parasitic worms in raw snail samples taken from the Shuguoyanyi restaurant branches. The parasite, Angiostrongylus cantonensis, was named after Guangzhou, where a Chinese doctor first found it in rats in 1933. Cases of infection from the worms have been found in other southern provinces such as Guangxi and Hainan since 1984.
The earliest cases of the current scare occurred in Beijing in late May, but authorities did not issue the warning until more cases were reported by local media. Symptoms include headaches, a stiff neck, low fever, skin irritation and nausea.
The Beijing Health Bureau and the local Industrial and Commercial Bureau said they would reinforce checks on markets and restaurants, cracking down on all fresh-water foods that failed to meet hygiene standards.