Risk factors for a hepatitis a outbreak in a building

Abstract

ObjectivesOn April, 2009, a hepatitis A outbreak occurred in a building. The outbreak was investigated to understand the characteristics of the outbreak and to clarify the risk factors.MethodsThe cases were defined as workers who worked in the building from February to April, 2009, they had medical evidence of hepatitis and they were positive on anti-hepatitis A virus (HAV) IgM antibody tests. This case-control study was conducted with 55 subjects (11 cases and their matched controls). The controls are matched according to gender, age and the employing company among the workers who were negative for IgG and IgM anti-HAV. The progress of the outbreak is described. Stool specimens were tested genetically. General characteristics were compared between the case and control groups. Common candidate risk factors were evaluated between the groups. The menus of the cafeteria at the building and the foods at the restaurants around the building were analyzed, respectively. ResultsThe outbreak lasted from March 23 to April 1, 2009. HAV was detected in only one stool specimen. The differences of general characteristics between the groups were not significant. The case group worked overtime significantly more frequently (Odds Ratio (OR) =1.63) than did the control group, but the other differences among the common factors were not significant. The intake of each cafeteria menu didn’t differ between the groups. The case group took significantly more leafy vegetables for wrapping (OR=8.81) among the foods eaten outside the building. The frequency of recent overtime work and the intake of leafy vegetables outside the building were still significant according to the multivariate analysis.ConclusionA higher frequency of overtime work and a greater intake of leafy vegetables at restaurants around the building increased the risk of infection during the HAV outbreak.