Erythema infectiosum in a village primary school: clinical and virological studies.

In a questionnaire response to an outbreak of erythema infectiosum in a village primary school, 55 (46%) of the 121 pupils reported an illness with rash. Three of the 12 members of staff also developed a rash. Onset in most affected children was indicated by the classical ;slapped cheek' appearance of erythema infectiosum with subsequent spread of the rash to the extremities. However, in 17 (35%) of 49 children who provided additional clinical data, the rash spread either in the reverse direction or not at all. Nineteen children (39%) reported recurrence of the rash.Serological studies confirmed that human parvovirus was the cause of the outbreak. Forty-six (44%) of 104 children investigated had significant levels of virus-specific immunoglobulin (lg)M and/or lgG antibodies consistent with recent infection. Most infections occurred in older children. Human parvovirus infection was also confirmed in five of the 12 adults. These studies revealed a substantial number of subclinical episodes - 14 (22%) of 64 subjects who remained well had serological evidence of recent infection with human parovovirus. Significantly, 43 individuals (37% of those investigated) remained seronegative despite frequent exposure to infection within the school. This finding, together with the observed temporary interruption of the outbreak which coincided with school holidays substantiates the view that human parvovirus has a relatively low infectivity and requires close person-to-person contact for its transmission.