Fast surveillance response reveals the introduction of a new yellow fever virus sub-lineage in 2021, in Minas Gerais, Brazil

BACKGROUND In Brazil, the yellow fever virus (YFV) is maintained in a sylvatic cycle involving wild mosquitoes and non-human primates (NHPs). The virus is endemic to the Amazon region; however, waves of epidemic expansion reaching other Brazilian states sporadically occur, eventually causing spillovers to humans. OBJECTIVES To report a surveillance effort that led to the first confirmation of YFV in NHPs in the state of Minas Gerais (MG), Southeast region, in 2021. METHODS A surveillance network was created, encompassing the technology of smartphone applications and coordinated actions of several research institutions and health services to monitor and investigate NHP epizootics. FINDINGS When alerts were spread through the network, samples from NHPs were collected and YFV infection confirmed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and genome sequencing at an interval of only 10 days. Near-complete genomes were generated using the Nanopore MinION sequencer. Phylogenetic analysis indicated that viral genomes were related to the South American genotype I, clustering with a genome detected in the Amazon region (state of Pará) in 2017, named YFVPA/MG sub-lineage. Fast YFV confirmation potentialised vaccination campaigns. MAIN CONCLUSIONS A new YFV introduction was detected in MG 6 years after the beginning of the major outbreak reported in the state (2015-2018). The YFV strain was not related to the sub-lineages previously reported in MG. No human cases have been reported, suggesting the importance of coordinated surveillance of NHPs using available technologies and supporting laboratories to ensure a quick response and implementation of contingency measures to avoid YFV spillover to humans.

Combination of surveillance tools reveals that Yellow Fever virus can remain in the same Atlantic Forest area at least for three transmission seasons

BACKGROUND In Brazil, the Yellow Fever virus (YFV) is endemic in the Amazon, from where it eventually expands into epidemic waves. Coastal south-eastern (SE) Brazil, which has been a YFV-free region for eight decades, has reported a severe sylvatic outbreak since 2016. The virus spread from the north toward the south of the Rio de Janeiro (RJ) state, causing 307 human cases with 105 deaths during the 2016-2017 and 2017-2018 transmission seasons. It is unclear, however, whether the YFV would persist in the coastal Atlantic Forest of RJ during subsequent transmission seasons. OBJECTIVES To conduct a real-time surveillance and assess the potential persistence of YFV in the coastal Atlantic Forest of RJ during the 2018-2019 transmission season. METHODS We combined epizootic surveillance with fast diagnostic and molecular, phylogenetic, and evolutionary analyses. FINDINGS Using this integrative strategy, we detected the first evidence of YFV re-emergence in the third transmission season (2018-2019) in a dying howler monkey from the central region of the RJ state. The YFV detected in 2019 has the molecular signature associated with the current SE YFV outbreak and exhibited a close phylogenetic relationship with the YFV lineage that circulated in the same Atlantic Forest fragment during the past seasons. This lineage circulated along the coastal side of the Serra do Mar mountain chain, and its evolution seems to be mainly driven by genetic drift. The potential bridge vector Aedes albopictus was found probing on the recently dead howler monkey in the forest edge, very close to urban areas. MAIN CONCLUSIONS Collectively, our data revealed that YFV transmission persisted at the same Atlantic Forest area for at least three consecutive transmission seasons without the need of new introductions. Our real-time surveillance strategy permitted health authorities to take preventive actions within 48 h after the detection of the sick non-human primate. The local virus persistence and the proximity of the epizootic forest to urban areas reinforces the concern with regards to the risk of re-urbanisation and seasonal re-emergence of YFV, stressing the need for continuous effective surveillance and high vaccination coverage in the SE region, particularly in RJ, an important tourist location.

Influence of breeding site availability on the oviposition behaviour of Aedes aegypti

Despite the importance of the mosquito Aedes aegypti in the transmission of arboviruses, such as yellow fever, Chikungunya fever and dengue fever, some aspects of their behaviour remain unknown. In the present study, the oviposition behaviour of Ae. aegypti females that were exposed to different densities of breeding sites (2, 4, 8 and 16) was evaluated in laboratory and semi-field conditions. The number of breeding sites that were used was proportional to the number available, but tended towards stabilisation. Females used four-six breeding sites on average, with a maximum of 11. A high percentage of eggs was observed in the water, along with the presence of a breeding site termed “favourite”, which received at least 40% of the eggs. The results are discussed in ecological, evolutionary and epidemiological approaches.

Study of oviposition behavior of aedes aegypti in two neighborhoods under the influence of semi-arid climate in the municipality of salinas, state of Minas Gerais, Brazil

The mosquito Aedes aegypti (Diptera: Culicidae) is the main vector of human arborvirus in Brazil.Oviposition behavior is important for the survival and dispersal of A. aegypti. The objective of this studywas to evaluate the oviposition behavior and its relationship to meteorological factors. Twenty ovitrapswere installed in two neighborhoods in the urban area of the city of Salinas, MG, southeastern Brazil.The traps were inspected weekly for the presence of eggs in the water and on the paddle. Simultaneously,regional weather data were analyzed. The results showed the Ovitrap Positivity Index (OPI) variedgreatly, from 0 to 90 percent, between the weeks and boroughs sampled, demonstrating the vector’s greatpopulation fluctuation. Among the analyzed climatic factors, rainfall strongly influenced oviposition,followed by relative air humidity. The number of eggs found on the paddle was significantly higher thanin the water (p<0.05). However, a significant increase of eggs in the water was noticed when the relativehumidity dropped below 40 percent. This seems to be an important behavior to maintain the population inperiods of drought. Through the low number of eggs (<30) found in 56 percent of positive traps, we concludedthat skip-oviposition behavior occurred, contributing to the prevalence of mosquitoes during thesampled period. It is concluded that the occurrence of water oviposition may be higher than described inthe literature, and should be studied due to its evolutionary and epidemiological importance...

O mosquito Aedes aegypti é o principal vetor de arborvírus humanos no Brasil. O comportamentode oviposição é importante para a sobrevivência e dispersão do A. aegypti. O objetivo deste trabalho foi avaliar estes comportamentos e sua relação com fatores climáticos. Instalaram-se vintearmadilhas ovitrampa em dois bairros de Salinas-MG. Todas foram inspecionadas semanalmentepara contagem e identificação dos ovos presentes na água e na palheta. Paralelamente, analisaram-sedados meteorológicos da região. Os resultados mostraram que o Índice de Positividade deOvitrampa (IPO) variou muito (0 por cento a 90 por cento) entre as semanas/bairros amostrados, o que demonstraa grande flutuabilidade populacional do vetor. Dentre os fatores climáticos analisados, o que maisintensamente influenciou a oviposição foi a precipitação, seguida da umidade relativa. O númerode ovos encontrados na palheta foi significativamente maior que na água (p<0,05). Entretanto,observou-se aumento significativo de ovos na água quando a umidade relativa esteve abaixo de 40 por cento.Este parece ser um dado importante para a manutenção das populações em períodos de seca. O baixonúmero de ovos (<30) encontrados em 56 por cento das armadilhas positivas demonstrou a ocorrência docomportamento de skip-oviposition que pareceu contribuir para a prevalência do mosquito em todoo período amostrado. Concluiu-se que a ocorrência de oviposição na água pode ser maior do que odescrito na literatura e deve ser investigada em virtude de sua importância evolutiva e epidemiológica...