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.
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.
Ciccone
Flávia Helena
FH
School of Public Health, University of São Paulo, São Paulo, SP.
Carvalhanas
Telma Regina Marques Pinto
TR
Afonso
Ana Maria Sardinha
AM
Flannery
Brendan
B
Waldman
Eliseu Alves
EA
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
D007075:Immunoglobulin M; D008458:Measles Vaccine