Last night, a seven-year-old girl was critically ill in hospital, and nearly 5,000 other children were sick after being poisoned by eel sushi in their school dinners, the latest in a series of unexplained food poisoning cases which have already killed four people since May.
Cleanliness and ritual purity occupy a central place in Japanese culture and religion, and the recent rash of poisonings has caused something close to panic.
In Sakai, a satellite city of Osaka where the latest outbreak has taken place, public swimming pools and all 92 schools have closed early for the summer holidays. Detergent manufacturers have reported a nationwide boom in sales of bleach and disinfectant, and cabinet ministers have been holding emergency meetings and flying in to comfort victims.
"We're here to find out what exactly brought this about and learn what we can do about it," the Health Minister, Naoto Kan, told reporters at a hospital in Sakai.
So far, though, the answers to those questions remain elusive. "Matters are not resolving themselves," said the mayor of Sakai, Hideo Hataya, yesterday. "They are getting worse." Since the first isolated cases were reported in May, the poisonings have harmed more people than last year's sarin nerve gas attack on the Tokyo subway.
The germ causing the havoc has been identified as O-157, a strain of the E bacoli bacteria which breeds in the human intestines, creating a toxin similar to the one which causes dysentery. A few hundred of the microscopic bacilli are enough to cause sickness.
Healthy adults usually recover from the illness, but children and the elderly are at grave risk. The early symptoms can be mild (in a previous case many young victims were sent home believing they had colds), but vomiting and bloody diarrhoea can lead to brain damage, kidney failure and death.
The bacilli can incubate for more than a week, making it difficult to track down exactly what food or liquid has been infected by them. The culprit in the recent case is believed to be a batch of eel sushi, prepared by Sakai's central school dinner depot on 5 July.
O-157 was discovered in the United States in 1982 and first appeared in Japan eight years later. Why then has it proved so difficult to eliminate? Responsibility, as so often here, appears to lie with the bureaucracy, and the inadequate co-ordination between local and national bodies.
"The terror posed by the outbreak of the O-157 colon bacillus is gripping the nation," the Yomiuri newspaper observed in a leader this week. "The health authorities are fully aware of the danger of this bacillus, but they have obviously failed to share their knowledge with doctors and school lunch officials at the local level."