ABSTRACT
An outbreak of enterohaemorrhagic Escherichia coli O157 occurred in multiple prefectures of Japan in November 2009. We conducted two case-control studies with trace-back and trace-forward investigations to determine the source. The case definition was met by 21 individuals; 14 (66.7%) were hospitalised, but no haemolytic uraemic syndrome, acute encephalopathy or deaths occurred. Median age was 23 (range 12-48) years and 14 cases were male (66.7%). No significant associations with food were found in a case-control study by local public health centres, but our matched case-control study using Internet surveys found that beef hanging tender (or hanger steak), derived from the diaphragm of the cattle, was significantly associated with illness (odds ratio = 15.77; 95% confidence interval, 2.00-124.11). Pulsed-field gel electrophoresis analysis of isolates from patients and the suspected food showed five different patterns: two in faecal and food samples, and another three in patient faecal samples only, although there were epidemiological links to the meat consumed at the restaurants. Trace-back investigation implicated a common food processing company from outside Japan. Examination of the logistics of the meat processing company suggested that contamination did not occur in Japan. We concluded that the source of the outbreak was imported hanging tender. This investigation revealed that Internet surveys could be useful for outbreak investigations.
Subject(s)
Disease Outbreaks , Escherichia coli Infections/epidemiology , Escherichia coli Infections/microbiology , Escherichia coli O157/isolation & purification , Foodborne Diseases/epidemiology , Foodborne Diseases/microbiology , Internet , Red Meat/microbiology , Adolescent , Adult , Animals , Case-Control Studies , Child , Electrophoresis, Gel, Pulsed-Field , Feces/microbiology , Female , Food Handling , Food Microbiology , Humans , Japan/epidemiology , Male , Middle Aged , RestaurantsABSTRACT
This report describes the assessment of the secondary attack rate (SAR) and the effectiveness of post-exposure antiviral prophylaxis among household contacts in the first domestic outbreak of a novel influenza A(H1N1)v between mid-May and early June 2009 in Kobe city, Japan. Of the 293 subjects, 14 (4.8%) household contacts met the case definition and most secondary cases were probably infected around the time of symptom onset date of the respective index case. The SAR among household contacts who did not receive prophylaxis was 7.6%, similar to the rate of seasonal influenza, and the attack rate in siblings was significantly higher than that in parents. We conclude that it is important to establish routine infection control measures for households in order to prevent the spread of the virus among household contacts and, possibly, to the community. We could not conclude whether antiviral prophylaxis was effective or not. However, among close contacts with underlying disease who received prophylaxis, nobody developed a severe form of the disease.
Subject(s)
Antiviral Agents/immunology , Disease Outbreaks , Influenza A Virus, H1N1 Subtype , Influenza, Human/epidemiology , Influenza, Human/prevention & control , Orthomyxoviridae Infections , Post-Exposure Prophylaxis/standards , Adolescent , Adult , Animals , Child , Child, Preschool , Female , Humans , Incidence , Infant , Japan/epidemiology , Male , Middle Aged , Young AdultABSTRACT
Between 9 May and 4 June 2009, a total of 401 laboratory-confirmed cases of influenza A(H1N1)v virus were reported in Japan, from 16 of the 47 Japanese prefectures. The two areas most affected were Osaka prefecture and Kobe city where outbreaks in high schools occurred leading to school closures. To date all cases have had symptoms consistent with seasonal influenza and no severe or fatal cases have been reported.
