Dengue virus (DENV) transmission by blood transfusion is an important route of viral acquisition during outbreaks. The prevalence of DENV markers (viral RNA, NS1, anti-DENV IgM, and IgG) among blood donors in Central-West Brazil has never been evaluated. Our aim was to evaluate the full set of serological and molecular markers for DENV among blood donors of the Federal District of Brazil during an extensive outbreak in 2016. We found an anti-DENV IgM prevalence of 6.74% (n = 32/475). Of 475, 20 samples (4.21%) were also anti-DENV IgG positive. All samples were non-reactive for NS1 and DENV RNA. Our results imply that a significant proportion of the tested donors had experienced asymptomatic infection. More studies are necessary to evaluate the real prevalence of DENV viremia in blood donors from the Federal District of Brazil and if specific measures are needed to routinely test the blood donors for DENV RNA during outbreaks.

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Background Vector-borne diseases, especially arboviruses transmitted by Aedes sp. mosquitos, should be a health policy priority in Brazil. Despite this urgency, there are significant limitations in the traditional surveillance system, mainly in vulnerable areas. This study aimed to investigate the circulation of dengue (DENV), Zika (ZIKV), and chikungunya viruses (CHIKV) by laboratory syndromic surveillance (LSS) in a slum area of the Federal District of Brazil, comparing the results with traditional surveillance data. Methods LSS for acute febrile and/or exanthematous symptoms was developed at a health unit of Cidade Estrutural, in order to identify the circulation of arboviruses transmitted by Aedes sp. mosquitos. Between June 2019 and March 2020, 131 valid participants were identified and sera tested by reverse transcription polymerase chain reaction (RT-PCR) for DENV (by serotype), ZIKV, and CHIKV acute infection and by immunoglobulin M enzyme-inked immunosorbent assay (ELISA-IgM) for DENV and CHIKV 15–21 days after symptom onset, when the participant reported no respiratory signs (cough and/or coryza). The results obtained were compared with traditional surveillance data for the study area and period. Results At least three DENV-1 (2.3%), four DENV-2 (3%), and one CHIKV (0.7%) cases were confirmed in the laboratory, showing evidence of hyperendemicity even though LSS had not reached the historic peak dengue fever months in the Federal District (April–May). When the results obtained here were compared with traditional surveillance, a significant discrepancy was observed, including underreporting of CHIKV infection. Conclusions In addition to the risks posed to the study population, the area investigated with its respective socio-environmental profile may be a potential site for spread of the virus, given the cosmopolitan presence of Aedes sp. and human mobility in the Federal District. It is also suggested that traditional epidemiological surveillance may be reporting acute viral infections other than DENV as dengue fever, while underreporting other arboviruses transmitted by Aedes sp. mosquitos in the Federal District. Graphical Abstract

Background: Mosquito-borne disease, especially arbovirus transmitted by Aedes mosquitoes, must be priority of Brazilian public health policies, mainly with others infectious agents in circulation. Laboratorial syndromic surveillance for fever or/and exanthematic acute syndrome was performed at health unit in slum area of Federal District. Methods: between June/2019 and March/2020, stopped by COVID-19 pandemic, 131 valid participants were identified and tested by RT-PCR for dengue (by serotype), chikungunya and Zika virus; and by serological IgM for dengue and chikungunya virus, with serologic assay performed when the participant did not present respiratory symptoms (cough or/and coryza). Results: 3 DENV-1 (2.3%), 4 DENV-2 (3%) and 1 CHIKV (0.7%) was lab-confirmed, showing evidence of hiperendemicity area even with the laboratorial syndromic surveillance not reaching the months of historical peak of dengue in Federal District (April-May). When compared the results of laboratorial syndromic surveillance with traditional epidemiologic surveillance data, is verified significant discrepancy between probable cases (from traditional surveillance) and lab-confirmed cases (from laboratorial syndromic surveillance). Conclusions: beyond the risks of local population are exposed, the socio-environment profile can be an able potential area to spread arbovirus, according to Aedes sp. dynamics and human mobility of the Federal District. Also, traditional surveillance may be misreporting probable cases for dengue infection, and underreporting confirmed cases for other arbovirus in the Federal District.

Background: Vector-borne diseases, especially arbiviruses transmitted by Aedes sp. mosquitos, should be a health policy priority in Brazil. Despite this urgency, there are significant limitations in the traditional surveillance system, such as lack of timely notification in identifying outbreaks at their onset and the systemic dismantling of entomological control in recent decades. Methods: Laboratory syndromic surveillance for acute febrile and/or exanthematous syndromes was developed at a health unit in a favela (Portuguese for slum) of the Federal District in order to identify the circulation of arboviruses transmitted by Aedes sp. mosquitos. Between June/2019 and March/2020, 131 valid participants were identified and tested by RT-PCR for dengue (by serotype), Zika and Chikungunya virus acute infection; and ELISA-IgM for dengue fever and Chikungunya 15-21 days after symptom onset, when the participant reported no respiratory signs (cough and/or coryza). The results obtained were compared with traditional epidemiological surveillance data for the study area. Results: At least 3 DENV-1 (2.3%), 4 DENV-2 (3%) and 1 CHIKV (0.7%) cases were confirmed in the laboratory, showing evidence of hyperendemicity even though laboratory syndromic surveillance had not reached the historic peak dengue fever months in the Federal District (April-May). When the results obtained here were compared with traditional epidemiological surveillance data, a significant discrepancy was observed, including underreporting of Chikungunya infection. Conclusions: in addition to the risks posed to the study population, the area investigated and its respective socioenvironmental profile may be a potential site for spreading the virus, given the cosmopolitan presence of Aedes sp. and human mobility in the Federal District. It is also suggested that traditional epidemiological surveillance may be notifying different acute viral infections such as dengue fever, while underreporting other arboviruses transmitted by Aedes sp. mosquitos in the Federal District.