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.

In Niterói, state of Rio de Janeiro, dengue virus type 4 (DENV-4) was isolated for the first time in March 2011. We analysed the laboratory findings of the first cases and evaluated the use of molecular techniques for the detection of DENV-4 in Aedes aegypti that were field-caught. Conventional reverse transcriptase-polymerase chain reaction (RT-PCR) and SimplexaTM Dengue real-time RT-PCR confirmed DENV-4 infection in all cases. Additionally, DENV-4 was confirmed in a female Ae. aegypti with 1.08 x 10³ copies/mL of virus, as determined by quantitative real-time RT-PCR. This is the first time the SimplexaTM Dengue real-time assay has been used for the classification of cases of infection and for entomological investigations. The use of these molecular techniques was shown to be important for the surveillance of dengue in humans and vectors.

Recently, we showed that infection with dengue virus increases the locomotor activity of Aedes aegypti females. We speculate that the observed increased locomotor activity could potentially increase the chances of finding a suitable host and, as a consequence, the relative biting rate of infected mosquitoes. We used a mathematical model to investigate the impact of the increased locomotor activity by assuming that this activity translated into an increased biting rate for infected mosquitoes. The results show that the increased biting rate resulted in dengue outbreaks with greater numbers of primary and secondary infections and with more severe biennial epidemics.

Roraima is the northernmost state of Brazil, bordering both Venezuela and Guyana. Appropriate climate and vector conditions for dengue transmission together with its proximity to countries where all four dengue serotypes circulate make this state, particularly the capital Boa Vista, strategically important for dengue surveillance in Brazil. Nonetheless, few studies have addressed the population dynamics of Aedes aegypti in Boa Vista. In this study, we report temporal and spatial variations in Ae. aegypti population density using ovitraps in two highly populated neighbourhoods; Centro and Tancredo Neves. In three out of six surveys, Ae. aegypti was present in more than 80% of the sites visited. High presence levels of this mosquito suggest ubiquitous human exposure to the vector, at least during part of the year. The highest infestation rates occurred during the peak of the rainy seasons, but a large presence was also observed during the early dry season (although with more variation among years). Spatial distribution of positive houses changed from a sparse and local pattern to a very dense pattern during the dry-wet season transition. These results suggest that the risk of dengue transmission and the potential for the new serotype invasions are high for most of the year.

Dengue tornou-se a mais importante doença viral transmitida por vetores no Brasil. O transporte humano de ovos resistentes à dessecação permitiu que seus dois mais importantes vetores, Aedes aegypti e Ae. albopictus, se tornassem cosmopolitas. Neste artigo, nós avaliamos a variação sazonal e espacial da abundância de larvas de Ae. aegyptie Ae. albopictus por meio de uma pequena escala espacial de zona de transição entre uma área urbana e uma área florestal do Rio de Janeiro, Brasil. Foram instaladas quarenta ovitrampas em cada área dos dez locais caracterizados por diferente densidade populacional humana e cobertura vegetal. Ovos e larvas foram coletados durante três semanas no verão e inverno de 2002 e 2003. Ae. albopictus foi predominantemente encontrado nas áreas com maior cobertura vegetal enquanto que nas áreas urbanizadas (comunidades), Ae. aegypti foi mais abundante. Ambas as espécies apresentaram pico durante a estação chuvosa. Esse padrão de distribuição das formas imaturas pode refletir no raio de vôo do adulto, favorecer a co-ocorrência de larvas dessas espécies nessa pequena escala espacial da zona de transição entre as áreas urbana e de floresta.

Dengue fever has become the most important vector-borne viral disease in Brazil. Human facilitated transport of desiccation-resistant eggs has led to its two most important vectors, Aedes aegypti and Ae. albopictus, becoming widespread. In this paper, we report seasonal and spatial variation in larval abundances of Ae. aegypti and Ae. albopictus across a small-scale transition zone between an urban area and an urban wooded/forested area within Rio de Janeiro, Brazil. We installed 400 ovitraps across 10 sites with different human population densities and vegetation coverage. Eggs and larvae were collected for three weeks during the wet and dry seasons of 2002 and 2003. Ae. albopictus was predominantly found in the forested areas of the study site whereas in the urbanized area Ae. aegypti was more abundant. Both species peaked during the wet season. This distribution pattern, which may reflect adult flight range, may favor the co-occurrence of larvae of these species in a small-scale urban/urban forest transition zone.

Dengue tornou-se a mais importante doença viral transmitida por vetores no Brasil. O transporte humano de ovos resistentes à dessecação permitiu que seus dois mais importantes vetores, Aedes aegypti e Ae. albopictus, se tornassem cosmopolitas. Neste artigo, nós avaliamos a variação sazonal e espacial da abundância de larvas de Ae. aegyptie Ae. albopictus por meio de uma pequena escala espacial de zona de transição entre uma área urbana e uma área florestal do Rio de Janeiro, Brasil. Foram instaladas quarenta ovitrampas em cada área dos dez locais caracterizados por diferente densidade populacional humana e cobertura vegetal. Ovos e larvas foram coletados durante três semanas no verão e inverno de 2002 e 2003. Ae. albopictus foi predominantemente encontrado nas áreas com maior cobertura vegetal enquanto que nas áreas urbanizadas (comunidades), Ae. aegypti foi mais abundante. Ambas as espécies apresentaram pico durante a estação chuvosa. Esse padrão de distribuição das formas imaturas pode refletir no raio de vôo do adulto, favorecer a co-ocorrência de larvas dessas espécies nessa pequena escala espacial da zona de transição entre as áreas urbana e de floresta.

Dengue fever has become the most important vector-borne viral disease in Brazil. Human facilitated transport of desiccation-resistant eggs has led to its two most important vectors, Aedes aegypti and Ae. albopictus, becoming widespread. In this paper, we report seasonal and spatial variation in larval abundances of Ae. aegypti and Ae. albopictus across a small-scale transition zone between an urban area and an urban wooded/forested area within Rio de Janeiro, Brazil. We installed 400 ovitraps across 10 sites with different human population densities and vegetation coverage. Eggs and larvae were collected for three weeks during the wet and dry seasons of 2002 and 2003. Ae. albopictus was predominantly found in the forested areas of the study site whereas in the urbanized area Ae. aegypti was more abundant. Both species peaked during the wet season. This distribution pattern, which may reflect adult flight range, may favor the co-occurrence of larvae of these species in a small-scale urban/urban forest transition zone.

Aedes albopictus é registrado pela primeira vez no estado de Roraima, Brasil. Entre junho de 2006 e maio de 2007 foram coletadas três pupas e dez larvas, duas das quais chegaram à fase adulta, durante atividades de vigilância rotineiras em três bairros urbanos da cidade de Boa Vista. Embora essa espécie não seja incriminada como vetor primário do dengue, a sua presença pode favorecer a ligação entre os ciclos silvestre e urbano da febre amarela e de outras arboviroses no Brasil.

Aedes albopictus is registered for the first time in Roraima, Brazil. From June 2006 to May 2007, three pupae and ten larvae of Ae. albopictus were collected, during routine surveillance work in three urban neighborhoods in the city of Boa Vista. Two larvae reached adulthood as females. Although Ae. albopictus is not presently considered of primary importance in dengue transmission, its occurrence could favor a linkage between urban and forest cycles of yellow fever and other arboviruses in Brazil.

Oral susceptibility and vertical transmission of dengue virus type 2 (DENV-2) in an Aedes albopictus sample from Rio de Janeiro was estimated. The infection (36.7%) and transmission (83.3%) rates for Ae. albopictus were higher than those of an Ae. aegypti colony used as control, 32.8 and 60%, respectively. Fourth instar larvae and females descendants of 48.5 and 39.1% of experimentally infected Ae. albopictus showed to harbor the virus. The oral susceptibility and the high capacity to assure vertical transmission exhibited by Ae. albopictus from Brazil reinforce that this species may play a role in the maintenance of the virus in nature and be a threat for dengue control in the country.

Como recentes estudos vêm incriminando diversas espécies de anofelinos como trasnmissores da malária na Amazônia brasileira além do Anopheles darlingi, realizamos um estudo sobre esse grupo de mosquitos em quatro localidades - Ariquemes, Cujubim, Machadinho e Itapoã do Oeste - no Estado de Rondônia, o mais malarígeno do país. Vinte espécies foram achadas. An. darlingi foi, de longe, a predominante e a única cuja densidade coincidiu com a da malária. Sugando iscas humanas, esse mosquito mostrou-se mais numeroso na imediata vizinhança das casas que em seu interior, onde, entretanto, foi quase a única espécie encontrada. Em ambas as situações picava principalmente ao crepúsculo vespertino e durante a primeira metade da noite, sendo menos freqüente longe das casas e escasso na floresta. Outras espécies, como An. triannulatus, An. evansae, An. albirarsis e An. strodei foram capturadas em números apreciáveis, somente em Ariquemes, em áreas com e sem malária, porém as demais mostraram-se raras. O An. darlingi foi confirmado como transmissor primário na área.

In view of recent studies incriminating several species of anophelines, besides Anopheles darlingi, as malaria vectors in the Brazilian Amazon, we performed an anopheline survey in four localities - Ariquemes, Cujubim, Machadinho and Itapoã do Oeste - in Rondônia, the most malarious State in the Country. Twenty species were found. An. darlingi was, by far, the dominant species and the only one whose density coincided with that of malaria. On human baits it was more numerous in the immediate vincinity of houses than indoors whre, however, it was almost the only species encountered. On both situations it fed mostly at sunset and during the first half of the night. It was less numerous far from houses and scarce inside the forest. Other species (An. triannulatus, An. evansae, An. albitarsis, An. strodei) appeared in appreciable numbers only in Ariquemes, both in areas with and without malaria. The remaining species were scanty. An. darlingi was confirmed as the primary local vector.