title: Challenges in Interpretation of Diagnostic Test Results in a Mumps Outbreak in a Highly Vaccinated Population.
abstract: In spite of a greatly reduced incidence rate due to vaccination, mumps outbreaks continue to occur in several areas of the world, sometimes in vaccinated populations. This article describes an outbreak in a highly vaccinated population in southwestern Ontario, Canada, and the challenges encountered in interpreting the results of diagnostic tests used in the outbreak. During the outbreak, patients were interviewed and classified according to the outbreak case definition, and specimens were collected for diagnostic testing according to Ontario guidelines. Twenty-seven individuals were classified as confirmed cases (n = 19) or suspect cases (n = 8) according to the case definition, only 9 of which were laboratory-confirmed cases: 7 confirmed by reverse transcriptase PCR (RT-PCR) and 2 by IgM serology. All 19 confirmed cases represented patients who were associated with secondary schools in the local area and had been vaccinated against mumps with one (n = 2) or two (n = 17) doses of the measles-mumps-rubella (MMR) vaccine. This is the first published report of an outbreak of mumps in Ontario in which all confirmed cases had been vaccinated against the disease. It highlights the limitations of and difficulties in interpreting current mumps diagnostic tests when used in vaccinated individuals.
authors.affiliation: Wellington-Dufferin-Guelph Public Health, Guelph, Ontario, Canada Lise.Trotz-Williams@wdgpublichealth.ca.
authors.forename: L A
authors.initials: LA
authors.lastname: Trotz-Williams
authors.affiliation: Wellington-Dufferin-Guelph Public Health, Guelph, Ontario, Canada.
authors.forename: N J
authors.initials: NJ
authors.lastname: Mercer
authors.affiliation: Wellington-Dufferin-Guelph Public Health, Guelph, Ontario, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Paphitis
authors.affiliation: Wellington-Dufferin-Guelph Public Health, Guelph, Ontario, Canada.
authors.forename: J M
authors.initials: JM
authors.lastname: Walters
authors.affiliation: Wellington-Dufferin-Guelph Public Health, Guelph, Ontario, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Wallace
authors.affiliation: Public Health Ontario, Public Health Laboratories, Toronto, Ontario, Canada.
authors.forename: E
authors.initials: E
authors.lastname: Kristjanson
authors.affiliation: Public Health Ontario, Public Health Laboratories, Toronto, Ontario, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Gubbay
authors.affiliation: Department of Microbiology, Mount Sinai Hospital, Toronto, Ontario, Canada.
authors.forename: T
authors.initials: T
authors.lastname: Mazzulli
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D003955:Diagnostic Tests, Routine / Q000379:methods*; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007075:Immunoglobulin M / Q000097:blood; D008297:Male; D008875:Middle Aged; D025202:Molecular Diagnostic Techniques / Q000379:methods; D009107:Mumps / Q000175:diagnosis* / Q000453:epidemiology*; D009108:Mumps Vaccine / Q000008:administration & dosage; D009864:Ontario / Q000453:epidemiology; D012367:RNA, Viral / Q000097:blood; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D055815:Young Adult
chemical_list: D007075:Immunoglobulin M; D009108:Mumps Vaccine; D012367:RNA, Viral
keywords: MMR; immunized population; mumps; mumps diagnostic tests; mumps serology; mumps vaccination