A school outbreak of parvovirus B19 infection investigated using salivary antibody assays

Abstract

An outbreak of parvovirus B19 infection at a primary school was investigated using saliva samples. Antibody capture immunoassays for salivary B19 IgG and IgM were developed using a recombinant B19 antigen and monoclonal antibody to B19 virus. Evaluation of the salivary IgG assay using paired serum and saliva samples from 43 staff at St Thomas' Hospital showed that it had a sensitivity of 100% and a specificity of 95%. Evaluation of the salivary B19 IgM assay using 87 paired blood and saliva samples from a study of general practitioner rubella notifications showed it had a sensitivity of 60% and a specificity of 98%. Using the salivary assay the level of B19 IgG within 2 weeks of the start of the outbreak ranged from 5-33% in children and 29% in staff. By detecting salivary B19 IgM and/or B19 IgG seroconversions, attack rates of 8-50% in children in different classes and 47% in staff were observed. Household transmission was also studied and an attack rate of 45% was recorded in 11 susceptibles. After the outbreak, the level of B19 IgG in children with the highest attack rates was 60-70%, similar to that seen in adults in the UK. This study highlights the risk of B19 infection in an institutional setting and shows that saliva samples are a useful alternative to blood.