Abstract

STUDY OBJECTIVE--To investigate a community wide outbreak of hepatitis A (HA). DESIGN--Description of the outbreak, with a case-control study to assess transmission. SETTING--A Florida county, USA, 1988-9. SUBJECTS--A total of 311 cases of HA. MEASUREMENTS AND MAIN RESULTS--A 13 month outbreak of HA is described. Most of the 311 cases (95%) were residents of a large metropolitan area (attack rate per 10,000 population (AR) = 3.7) and two smaller cities (AR = 61.5 and AR = 6.4). The ARs were greater for males than females and for residents aged 25-34 years (9.7) and < 5 years (8.3). Altogether 37% of cases were linked to day care centres, independent of the city of residence. A household case-control study showed an increased risk of HA in households in which a child attended a day care centre (p = 0.02), and centres that could take more than 50 children had an increased risk of HA introduction than smaller ones (p = 0.05). CONCLUSIONS--Day care centres were an important source of HA in the community, and the need for timely surveillance and immunoglobin prophylaxis is emphasised. Homosexual transmission may have played an important role in this outbreak.