Busca ativa retrospectiva por infecções precoces pelo vírus chikungunya em Alagoas entre 2013 e 2014

Abstract

Chikungunya (CHIKV) is an arbovirus transmitted by vectors of the genus Aedes. The CHIKV virus is an Alphavirus, belonging to the Togaviridae family. It was isolated for the first time in Tanzania, in 1952-53, where it caused local outbreaks, but it has been spread across the world in the past two decades. It is an emerging virus in Brazil, initially associated with imported cases, but which has been established in an endemic way in the country, in very recent years. Local transmission of CHIKV was detected in Brazil for the first time in September 2014. Since 2015, Alagoas has been officially registering cases of human infections by CHIKV, although CHIKV infection can be identified mainly by detection of viral RNA and serology for antibody research, the diagnosis of most cases has been made only clinically. Although rapid arbovirus infections have assumed an important role in recent years in Brazil, there are difficulties and lack of laboratory methods capable of confirming the etiological diagnosis of infections by different arboviruses. This group of viruses causes disease with similar symptoms, leading to underreporting of CHIVK and inaccurate data on the real period of entry of the disease in Alagoas. The aim of this work was to investigate the occurrence of CHIKV infections in Alagoas between the years 2013 and 2014, retrospectively. For the survey, it was selected 44 serum samples from a biorrepository, which had been collected from individuals with suspicion of dengue in the years 2013 and 2014, previously tested and negative for dengue and other flavivirus. Among the samples, some were collected in the acute phase of febrile illness (<7 days from the onset of symptoms) and others in the convalescent phase (> 7 days). Samples were screened for confirmation of CHIKV infection using serology, RT- PCR and viral isolation in cell culture. Anti-CHIKV IgM and IgG antibodies were found in 2 and 4 samples, respectively, that were collected between June and September 2014. CHIKV was successful isolated in C6/36 cells from one IgM-positive serum sample (collected in August 2014). The specie CHIKV was confirmed by RT-PCR of the cells supernatant and by immunofluorescence for viral antigen detection. The strain of this clinical isolate was called CHIKV Mcz630. Overall, our serology and viral isolation data - obtained from serum samples collected in 2014 - demonstrate that CHIKV was already present in the state of Alagoas since that year, and not only since 2015, as attest official data. These results even suggest that CHIKV emerged in Alagoas before the first report of the autochthonous infection of CHIKV in Brazil.