Silent circulation of Zika and dengue virus in Aedes aegypti (Diptera: Culicidae) during a non-epidemic year in the state of Sergipe, northeastern Brazil.

BACKGROUND: Dengue virus (DENV) and Zika virus (ZIKV) have a severe impact on human health worldwide. To understand the dynamics of these viruses in mosquito populations, it is necessary to maintain surveillance during non-epidemic years. METHODS: We aimed to assess the presence of DENV and ZIKV in Aedes aegypti females in the state of Sergipe, northeastern Brazil, during a non-epidemic year. The Ae. aegypti females collected were sectioned, and the heads and thorax were used to analyze the infection rate. Each female was first analyzed to detect Flavivirus using RT-PCR. Flavivirus-positive samples were further screened to detect ZIKV and DENV types 1, 2, 3 and 4. RESULTS: A total of 184 females were collected. ZIKV was identified in 5.4% of the sample and DENV in 7.1%, with the DENV-positive samples belonging to subtypes 2, 3 and 4. The presence of coinfected vectors was also observed. Of the four cities tested, only one was negative for all viruses. CONCLUSIONS: These results show that the maintenance of vigilance during non-epidemic years can provide data on viruses circulating before the onset of outbreaks. This can enable the planning and implementation of local control measures to prevent the appearance of new outbreaks.

Molecular characterization and phylogenetic analysis of Chikungunya virus during the 2016 outbreak in Sergipe, northeastern Brazil.

BACKGROUND: Chikungunya (CHIKV) is an arbovirus transmitted mainly by Aedes aegypti females. CHIKV has been highlighted as the pathogen with the greatest impact due to the high morbidity caused by the infection. In 2016, Brazil experienced an outbreak that affected almost 272 000 people. Here, we performed a molecular characterization and phylogenetic analysis of the CHIKV circulating in 2016 in the state of Sergipe, Brazil. METHODS: A partial region of the E1 gene of 16 CHIKV-positive samples from Sergipe State was amplified and sequenced. RESULTS: All sequences belonged to the East-Central-South-African genotype and three point mutations were verified. Two of them were silent mutations and one was a non-synonymous mutation, which changed lysine to threonine at position 211 in the E1 protein. This mutation was present in 81.2% of the sequences, as well as in other five Brazilian sequences from previous studies. This study found that CHIKV strains circulating in Sergipe during the 2016 outbreak belonged to two different haplotypes. CONCLUSIONS: The strains circulating in Sergipe are phylogenetically close to other Brazilian samples circulating in the northeast and southeast of the country, as well as viruses circulating during the same period in Haiti, indicating the rapid spread of these haplotypes.