title: Mumps outbreak and laboratory diagnosis.
abstract: BACKGROUND
  Several mumps outbreaks have been reported in Europe and in the United States among highly vaccinated populations. Biological diagnosis is classically based on the detection of mumps-specific IgM, but the ability of serological tests to confirm mumps infection seems to be limited among vaccinated patients.
  
  
  OBJECTIVE
  We aim to report a mumps outbreak in an engineering school in Grenoble, France, from February to June 2013 and results of the biological testing.
  
  
  METHODS
  WHO definitions were used to define cases. Mumps--specific IgM and IgG were assessed by a commercially available EIA. Mumps RNA detection by real time reverse transcriptase polymerase chain reaction tests (RT-PCR) and mumps genotyping were performed by the French National Reference Centre for Paramyxoviridae.
  
  
  RESULTS
  Sixty two mumps patient-cases were identified using WHO case definitions, 20 being biologically explored, of which 17 were confirmed by biological tests. Vaccination status was documented for 27 patients/62: 4 (14.8%) patients had received one dose of MMR vaccine, and 23 (85.2) two doses of MMR vaccine. Among the biologically explored patients, 83% had a positive RT PCR at the first sampling whereas only 45% had positive or equivocal IgM. All the genotyped strains were genotype G.
  
  
  CONCLUSIONS
  Mumps laboratory diagnosis in a highly vaccinated population is challenging. Serological tests among vaccinated patients should be interpreted cautiously and confirmed by RT-PCR tests at the beginning of a mumps outbreak.
authors.affiliation: Infectious Diseases Department, Grenoble University Hospital, France. Electronic address: mmaillet@chu-grenoble.fr.
authors.forename: Mylène
authors.initials: M
authors.lastname: Maillet
authors.affiliation: Inter-University Health Center, Grenoble, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Bouvat
authors.affiliation: Inter-University Health Center, Grenoble, France.
authors.forename: Nicole
authors.initials: N
authors.lastname: Robert
authors.affiliation: Virology Department, Grenoble University Hospital, France. Electronic address: mbaccard@chu-grenoble.fr.
authors.forename: Monique
authors.initials: M
authors.lastname: Baccard-Longère
authors.affiliation: Virology Department, Grenoble University Hospital, France. Electronic address: cmorel-baccard@chu-grenoble.fr.
authors.forename: Christine
authors.initials: C
authors.lastname: Morel-Baccard
authors.affiliation: Virology Department, Grenoble University Hospital, France; Unit of Virus Host Cell Interactions UMI 3265 UJF-EMBL-CNRS, Grenoble, France. Electronic address: pmorand@chu-grenoble.fr.
authors.forename: Patrice
authors.initials: P
authors.lastname: Morand
authors.affiliation: National Reference Centre for Paramyxoviridae, Caen University Hospital, France. Electronic address: vabret-a@chu-caen.fr.
authors.forename: Astrid
authors.initials: A
authors.lastname: Vabret
authors.affiliation: Infectious Diseases Department, Grenoble University Hospital, France. Electronic address: jpstahl@chu-grenoble.fr.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Stahl
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D004196:Disease Outbreaks; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D008297:Male; D022542:Measles-Mumps-Rubella Vaccine / Q000276:immunology; D008828:Microbiological Techniques; D058889:Molecular Typing; D009107:Mumps / Q000175:diagnosis* / Q000453:epidemiology* / Q000517:prevention & control; D009109:Mumps virus / Q000145:classification / Q000235:genetics; D012621:Seasons; D012703:Serotyping; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral; D022542:Measles-Mumps-Rubella Vaccine
keywords: Mumps outbreak; Mumps reverse transcriptase polymerase chain reaction; Mumps serological test; Mumps vaccine