In addition, if the etiological agent is EHEC, Vibrio cholerae O1&O139, Shigella , S . Typhi or S . Paratyphi A, the physician must notify as the case of the category III infectious disease in compliance with the Infectious Diseases Control Law.
1. Incidence of bacterial food poisoning: According to the Statistics of Food Poisoning published by the Food Safety Division, the Ministry of Health, Labour and Welfare (MHLW) (http://www.mhlw.go.jp/topics/syokuchu/04.html), the incidents peaked at 2,620 involving 36,337 cases in 1998, and the decreasing tendency continued until 2007, during which time cases counted at 9,666, below 10,000, in 2006 (Table 1). Food poisoning due to Vibrio parahaemolyticus or Salmonella was on the marked decrease (see IASR 27: 191-192, 2006) and that due to pathogenic E. coli was also decreasing (Fig. 1 and Fig. 2). In contrast, incidents of Campylobacter jejuni/coli food poisoning have increased largely due to the increasing reports of single-case incidents after 1997 without accompanying such marked increase in cases (IASR 27: 167-168, 2006). Cases of Staphylococcus aureus food poisoning suddenly increased due to a large-scale outbreak occurring in 2000, after then kept on a level of 1,000-2,000 without large increase in incidents. Although there were increase and decrease in cases of EHEC, Clostridium perfringens and Bacillus cereus food poisoning, no marked increase was seen in incidents. However, notified cases of EHEC infections based on the Infectious Diseases Control Law largely outnumbered EHEC food poisoning cases every year (IASR 29: 117-118, 2008). In many incidents, identification of incriminated food item was difficult and single-case incidents may not have been notified as food poisoning.
2. Large-scale outbreaks: Twenty-six incidents of bacterial food poisoning involving ≥500 cases, a prospect of a large-scale incident, occurred during 1998-2007 (Table 2). The etiological agents were Salmonella spp. in 8 outbreaks, C. perfringens in 6, V. parahaemolyticus in 5, pathogenic E. coli in 4, S. aureus in 2, and B. cereus in 1. After 2002, large-scale outbreaks due to C. perfringens are noticeable (see p. 216-219 of this issue).
Diffuse outbreaks occurring in many prefectures have been 1) Salmonella food poisoning (1,634 cases, mainly children) due to semidried squid snacks distributed in the whole country (IASR 21: 162-163, 2000), 2) S. aureus food poisoning due to low-fat milk (13,420 cases, the largest scale ever occurred in Japan after the end of World War II) (IASR 22: 185-186, 2001), and 3) V. parahaemolyticus food poisoning due to salted squid of low salt concentration (620 cases in Tokyo Metropolis, 5 prefectures and 6 designated cities) (see p. 219 of this issue).
In 2007, large-scale EHEC food poisoning, although involving less than 500 cases, occurred due to meals served at a school refectory (445 cases) (IASR 29: 120-121, 2008) and due to boxed lunches served by a restaurant (314 cases) (IASR 29: 122-123, 2008).
3. New noteworthy etiological agents of food poisoning
1) Listeria monocytogenes : Such milk products as natural cheese and meat products have been reported as causative foods. In Japan, L. monocytogenes was detected in imported cheese and the products were recalled before occurrence of incident. Retrospective studies conducted by the study group of MHLW since 2001 have reported about 83 sporadic cases per year on average (see p. 222 of this issue). An outbreak occurring in Hokkaido due to domestic natural cheese has been the only one ever reported (Int. J. Food Microbiol. 104: 189-196, 2005).
2) Enterobacter sakazakii : In other countries, 73 incidents of infection of infants involving 27 deaths due to powdered infant formula (PIF) were reported, and there was an incident that highly contaminated PIF was withdrawn (see p. 223 of this issue). In Japan, a single case of infection from other food than PIF has been reported (Japan Society of Perinatal and Neonatal Medicine 2007). MHLW, in compliance with the guidelines of WHO/FAO (http://www.who.int/foodsafety/publications/micro/pif_guidelines.pdf), gave a note in the maternity and child health record books distributed after April 2008, recommending to use lukewarm water once boiled and not below 70°C for reconstituting PIF (http://www.mcfh.or.jp/jouhou/fukudokuhon/70-71.html).
Conclusion: The incidence of bacterial food poisoning has been on the decrease, whereas diffuse outbreaks are occurring and so are deaths almost every year, which requires special attention. Thorough food sanitation management is necessary for manufacturers, distributors, retailers, and consumers. Besides, there may be more complaints of suspected food-borne illness without identification of etiological agent than notified food poisoning cases. Only limited prefectural and municipal public health institutes and health centers practice the tests for the pathogenic factors of pathogenic E. coli (see p. 224-228 of this issue), and ensuring investigation and laboratory examination systems for identification of etiological agents are desired.