【Reading】のろういるす

【English Name】Norovirus

The pathogen most feared in terms of hygiene at sushi restaurants and throughout the food-service industry is norovirus. It is a frequent cause of food poisoning and infectious gastroenteritis, and in Japan's 2024 (Reiwa 6) statistics it accounted for roughly 60% of all food-poisoning patients. Outbreaks are concentrated every year from November through the following March.

It is an RNA virus belonging to the family Caliciviridae, with a particle diameter of around 30–38 nm. Because it lacks an envelope, it is difficult to inactivate with disinfectant alcohol, and infection can occur from as few as 10 to 100 virus particles entering the body.

The existence of this virus came to light following an outbreak of mass gastroenteritis in Norwalk, Ohio, in the United States in 1968, and in 2002 the International Committee on Taxonomy of Viruses officially established its current name.

In relation to sushi, the property by which bivalves such as oysters concentrate and take in viruses from seawater through filter feeding has long been regarded as a problem. However, the recent trend is that cases in which shellfish are definitively identified as the source are decreasing, and the majority of cases involve food being contaminated via the hands of food handlers.

The incubation period after infection is generally 24–48 hours, after which vomiting, diarrhea, and abdominal pain develop. A healthy adult usually recovers in about 1–2 days. The keys to prevention are thorough hand washing and disinfection using sodium hypochlorite, and at sushi restaurants that handle raw ingredients, monitoring the health of workers and carefully washing cooking utensils are indispensable.