Seroprevalence of antibodies to pandemic (H1N1) 2009 influenza virus among health care workers in two general hospitals after first outbreak in Kobe, Japan.

OBJECTIVE: To assess the prevalence including asymptomatic infection, infection risk of exposure to patients, and effectiveness of personal protective equipment (PPE) among health care workers (HCWs) during the first pandemic (H1N1) 2009 (pH1N1) outbreak in Kobe, Japan in May 2009. METHODS: A cross-sectional seroepidemiological study was conducted on 268 HCWs in the two hospitals in Kobe to which all pH1N1 inpatients were directed. Participating HCWs completed a self-administrated questionnaire and provided a single serum sample which was analyzed using a hemagglutination-inhibition (HI) antibody test. RESULTS: Of 268 subjects, 14 (5.2%) were found to have positive antibodies to the pH1N1 by HI assay; only 1 reported a febrile episode. Among the 14 seropositive cases, 8 received chemoprophylaxis. 162 HCWs (60.4%) had been exposed to patients. The seropositive rate (SPR) for pH1N1 of the exposed group was higher than that of the unexposed group, however not statistically significant (6.8% vs. 3.1%, p = 0.197). There were no statistically significant differences in SPR for any PPE. CONCLUSION: The SPR for pH1N1 in the exposed group was higher than that of the unexposed group in HCWs; however, most of these individuals were asymptomatic. There was no statistically significant association between PPE implementation and pH1N1 seropositivity.