title: Investigation of measles IgM-seropositive cases of febrile rash illnesses in the absence of documented measles virus transmission, State of São Paulo, Brazil, 2000-2004.
abstract: BACKGROUND
  To review measles IgM-positive cases of febrile rash illnesses in the State of São Paulo, Brazil, over the five-year period following interruption of measles virus transmission.
  
  
  METHODS
  We reviewed 463 measles IgM-positive cases of febrile rash illness in the State of São Paulo, from 2000 to 2004. Individuals vaccinated against measles < or = 56 days prior to specimen collection were considered to be exposed to the vaccine. Serum from the acute and convalescent phases was tested for evidence of measles, rubella, parvovirus B19 and human herpes virus-6 infection. In the absence of seroconversion to measles immunoglobulin-G, measles IgM-positive cases were considered false positives in individuals with evidence of other viral infections.
  
  
  RESULTS
  Among the 463 individuals with febrile rash illness who tested positive for measles IgM antibodies during the period, 297 (64%) were classified as exposed to the vaccine. Among the 166 cases that were not exposed to the vaccine, 109 (66%) were considered false positives based on the absence of seroconversion, among which 21 (13%) had evidence of rubella virus infection, 49 (30%) parvovirus B19 and 28 (17%) human herpes virus-6 infection.
  
  
  CONCLUSIONS
  Following the interruption of measles virus transmission, thorough investigation of measles IgM-positive cases is required, especially among cases not exposed to the vaccine. Laboratory testing for etiologies of febrile rash illness aids interpretation of these cases.
authors.affiliation: School of Public Health, University of São Paulo, São Paulo, SP.
authors.forename: Flávia Helena
authors.initials: FH
authors.lastname: Ciccone
authors.forename: Telma Regina Marques Pinto
authors.initials: TR
authors.lastname: Carvalhanas
authors.forename: Ana Maria Sardinha
authors.initials: AM
authors.lastname: Afonso
authors.forename: Brendan
authors.initials: B
authors.lastname: Flannery
authors.forename: Eliseu Alves
authors.initials: EA
authors.lastname: Waldman
mesh_terms: D001938:Brazil / Q000453:epidemiology; D005076:Exanthema / Q000175:diagnosis* / Q000453:epidemiology; D005189:False Positive Reactions; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood* / Q000276:immunology; D008457:Measles / Q000175:diagnosis* / Q000453:epidemiology / Q000517:prevention & control; D008458:Measles Vaccine / Q000276:immunology*; D008459:Measles virus / Q000276:immunology*; D010322:Parvoviridae Infections / Q000175:diagnosis / Q000453:epidemiology; D011159:Population Surveillance; D019349:Roseolovirus Infections / Q000175:diagnosis / Q000453:epidemiology; D012409:Rubella / Q000175:diagnosis / Q000453:epidemiology
chemical_list: D007075:Immunoglobulin M; D008458:Measles Vaccine