Epidemiologic and diagnostic evaluation of a recent mumps outbreak using oral fluid samples.

OBJECTIVE: To determine the optimal strategy to investigate mumps virus infection in a partially vaccinated cohort. STUDY DESIGN: 122 oral fluid and serum samples were collected in a recent outbreak in Ireland. The largest age cohort, students aged 18-21 years old attending third level institutions, were investigated using virus isolation, detection of mumps specific IgM, IgG, RT-PCR and molecular genotyping. RESULTS: 97% of patients had both detectable serum IgM and IgG. Mumps virus RNA was detected in 17 oral fluid samples and 14 of these originated from a single geographic location. Only 6 of the IgM positive samples had detectable mumps virus RNA whereas this could be detected in 11 IgM negative samples. Genotyping studies revealed that genotypes G and J were co-circulating during this outbreak. CONCLUSIONS: The use of an oral fluid sample to detect mumps virus RNA and IgM offers a major improvement over serological diagnosis in acute infection in both non-vaccinated or partially vaccinated individuals, and has the advantage that specimens are collected non-invasively.