Shredded dried laver seaweed caused a wave of food poisoning that affected more than 1,000 children and teachers at seven elementary schools in Tachikawa on the outskirts of Tokyo from Feb. 17.
The norovirus was detected in the “nori” that was served in school meals on Feb. 16, the Tokyo metropolitan government announced Feb. 28.
In Tachikawa, 1,098 victims had complained of diarrhea and vomiting as of noon Feb. 24.
Another outbreak occurred in Wakayama Prefecture, western Japan, in January due to nori provided by the same maker as in the Tachikawa case.
The shredded nori was provided by Tokaiya Co., which is headquartered in Osaka’s Miyakojima Ward. Tokaiya is voluntarily recalling products that may be affected.
The seaweed in the Tachikawa case was used as a topping for a bowl of rice covered with a mixture of chicken and eggs.
A study by the metropolitan government’s food surveillance department showed that the virus gene type detected from the packaged nori matched that from the sampled stools of victims.