GENOTYPING OF MUMPS VIRUS IN CANADA

Objectives:Mump virus causes an acute illness characterized by unilateral or bilateral parotitis, fever and headache. Orchitis is a rare complication in males. Meningoencephalitis is also a rare serious complication. Since the introduction of the mumps vaccine in 1969 and then subsequently the MMR (mumps–measles–rubella) vaccine, cases of mumps have decreased dramatically although it is not uncommon for sporadic cases to occur. In 2007, a mumps outbreak occurred in Canada. Mumps virus genotyping is useful for molecular epidemiologic purposes. The purpose of this study is to describe the mumps virus strains detected in Canada.

Design: Clinical specimens including oral specimens and urine were collected from suspected mumps cases. Total nucleic acid was extracted and RT-PCR (F gene target) performed as a diagnostic assay. Positive samples were then amplified by RT-PCR targeting the SH gene followed by sequencing. Sequence data were analyzed and compared to mumps virus reference strains.  

Results: The predominant strain causing the 2007 mumps outbreak in Canada was determined to be genotype G. Two small clusters of different genotype G subtypes were detected within the overall outbreak indicating distinct importations unrelated to, but concurrent with the larger outbreak. Additional genotypes (H and D) were also detected in imported sporadic cases.

Conclusions: Mumps virus genotyping data was used to distinguish sporadic cases from the outbreak cases as well as determine distinct clusters within the outbreak. Mumps virus genotyping is useful for molecular epidemiologic purposes such as differentiating vaccine and wild-type strains, linking cases, linking outbreaks, tracking importations, and documenting the elimination of a particular strain from a geographic area.