Os casos que não se confirmaram como dengue durante a epidemia de dengue no municipio de Campinas/SP, 2002 / Unconfirmed dengue cases during the Campinas dengue epidemic of 2002

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

In 2002 the city of Campinas, SP, Brazil reported its greatest dengue epidemic. The Epidemiological Surveillance System received about 10,000 notifications of possible dengue cases. Over 70% of the cases were not confirmed by laboratory methods (MAC-ELISA, performed at the Instituto Adolfo Lutz, the state public health laboratory). During the peak of the outbreak, one adult died. The initially suspected diagnosis of dengue haemorrhagic fever was not confirmed, and a diagnosis of a spotted fever group rickettsiosis was confirmed by indirect immunofluorescent antibody assay and polymerase chain-reaction (PCR). Due to the high number of unconfirmed cases and the death by spotted-fever, two hypotheses were raised: either an overlapping, unsuspected epidemic or an inadequacy in the laboratory diagnosis. In order to clarify these issues, a posteriori of the epidemics, an epidemiological analysis was performed comparing the confirmed and unconfirmed cases, taking into consideration the time interval between the onset of symptoms and serologic investigation, among patients living in the municipality of Campinas who started having symptoms from January 1st through October 7th, 2002. The data source was SINAN-W, the national web-based data bank of notified diseases. Stored sera, negative for dengue fever, were tested again for dengue (MAC-ELISA, commercial reagent) and for rickettsial infection both typhus and spotted fever groups (indirect immunofluorescent antibody assay). Neither the epidemiological analysis nor the serological were able to suggest a parallel outbreak of rickettsial disease or that there had been an excessive amount of false-negative dengue tests. In only eight percent of the initially negative sera for dengue fever the presence of specific antibody was demonstrated, a proportion not sufficient to support the hypothesis of an inadequate laboratorial diagnosis. However, the possibility of an overlapping epidemic of an unknown nature could not be excluded. An explanation for the unconfirmed cases would be an over-zealous tendency to notify any fever as dengue during an epidemic.The need for more a more sensitive epidemiological surveillance system becomes obvious when investigating diseases with similar clinical symptoms, making an adequate differential diagnoses difficult. Syndrome-based surveillance systems are possibly better for situations such as these. It became obvious that current routine surveillance is not adequately sensitive and does not discriminate between all possibilities, leaving public health officials with a large amount of unanswered questions, like the one presently discussed. Other surveillance tools should be employed to increase the sensitivity of current methods. Geographical information systems should be introduced in the routine surveillance work. Current procedures are inadequate to cope with a dynamic epidemiological context, particularly when we regard the emerging infectious diseases.

ASSUNTO(S)

dengue - contole vigilancia epidemiologica disease outbreak epidemiologia epidemias doenças transmissiveis epidemiology epidemiologic surveillance communicable diseases dengue control

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