Parvovirus outbreak in a kindergarten in a municipality in the north of Portugal, April-June 2008.

In response to an alert raised due to epidemic exanthematous rashes in children in a kindergarten, an outbreak investigation was carried out in a municipality in the north of Portugal in late spring 2008. The intention was to establish an aetiological diagnosis and take corrective measures if necessary. The warden at the kindergarten was interviewed, and a self-administered questionnaire was given to parents and staff. Blood samples from seven children with facial erythema were collected for serological investigation. Seventeen cases of erythema infectiosum, due to infection with parvovirus B19, were identified and classified as "confirmed". No cases occurred among the eight adult staff members. An overall attack rate of 38% was observed among the 45 children (born in 2002 and 2003). All cases were mild and without fever. This parvovirus B19 outbreak made it possible to estimate the basic reproduction number (R0) at between 6 and 8 (or above). Staff members, parents and local clinicians were informed that the infection could pose a risk when caught by people with special clinical conditions. All children had received one dose of measles-mumps-rubella vaccine and 60% had received two doses. The seven children with serologically confirmed parvovirus B19 infection were immune to measles and rubella. All seven were negative for measles- or rubella-specific IgM.