An outbreak of cryptosporidiosis suspected to be related to contaminated food, October 2006, Sakai City, Japan.

On October 17, 2006, the Sakai City Public Health Center received a report of acute gastroenteritis among 4 members from the same company who had eaten raw meat dish called "Yukke: Korean-style beef tartar" and raw liver at a rotisserie in Sakai City on October 7. Based on information from interviews, the median incubation period was 5.5 (range, 5-7 days), and the median length of illness was 7 days (range, 4-10 days). The illness was characterized by a prolonged incubation period, non-bloody watery diarrhea, reduced vomiting, and light fever, which led us to suspect an enteric protozoan infection. Stool specimens obtained from 3 of the 4 symptomatic patients were positive for Cryptosporidium oocysts. They, along with 2 food workers, were negative for food poisoning bacteria or Norovirus. Genotyping of the Cryptosporidium isolates by direct sequencing of PCR products revealed that all the isolates were the C. parvum genotype II (bovine) and the subgenotype of IIa with 100 % homology with respective 18S rRNA and Cpgp40/15 genes. Positive implementation of tests for enteric protozoa including Cryptosporidium is necessary in the differential diagnosis of suspected foodborne gastroenteritis, particularly when it is characterized by a prolonged incubation period and severe watery diarrhea. In fact, we were able to diagnose the illness as cryptosporidiosis without waiting for the results of bacteriological and virological examinations, and thus prevented the possible occurrence of a secondary infection through an ill patient who works as cooking personnel in the company.

Combined genogroup I and II norovirus infection at a nursery.

From November 2004 to April 2005, 5 cases of norovirus (NoV) occurred in Sakai City, Japan. These were all diffuse outbreaks due to infections with genogroup II genotype 4 (GII/4) virus strains. Similar outbreaks occurred throughout Japan; hence, GII/4 was assumed to be the prevalent NoV type. However, a NoV outbreak that occurred at a nursery in May 2005, was caused by infections with GI/4 and GII/6 viruses, respectively, from different children. The time course of newly infected patients showed that this nursery outbreak had a two-peak pattern, with the peak numbers of patients occurring on May 19 and May 22. Virological examination and epidemiological research could not determine whether the GI and GII NoV infections occurred at the same time, or whether there was a time difference in their appearance in the nursery. From this outbreak, it is clear that the timing of obtaining samples and obtaining the minimal necessary number of primary samples are essential for accurate epidemiological information to be obtained. In addition, we detected genotypes that were different from the previously prevalent genotypes, which raises the possibility of more frequent NoV infection or a change in the prevalent NoV genotype in this setting. In conclusion, it is difficult to predict outbreaks of NoV; however, through vigilant and early collection and analysis of later samples throughout an outbreak, it is possible to understand the prevalence and perhaps trace the source of NoV infections.