Isolations of yellow fever virus from Haemagogus leucocelaenus in Rio Grande do Sul State,Brazil

Following howling monkey (Alouatta caraya) deaths and yellow fever (YF) antigen detection by immunohistochemistry in the liver sample of a dead monkey in April and May 2001 in the municipalities of Garruchos and Santo Ant?nio das Miss?es, Rio Grande do Sul State, Brazil, epidemiological field investigations were initiated. Two strains of YF virus were isolated in suckling mice from 23 Haemagogus (Conopostegus) leucocelaenus Dyar & Shannon mosquitoes collected from the study sites. The YF virus was isolated from this species in the 1930s in Brazil and in the 1940s in Colombia. No human cases were reported during the current epizootic outbreak. The YF virus isolation and the absence of Hg. (Haemagogus) janthinomys Dyar from the area suggest that Hg. leucocelaenus may be a secondary YF vector and play an important role in the epidemiology of this disease in the Southern Cone.     

Isolation and characterization of wild type yellow fever virus in cases temporally associated with 17DD vaccination during an outbreak of yellow fever in Brazil

A mass vaccination was carried out in the state of Minas Gerais, Southeast region of Brazil, to control an outbreak of sylvatic yellow fever in 2001. During the outbreak the surveillance system identified two fatal cases temporally associated with YF vaccination. Virus recovered from blood and postmortem samples of both cases was identified as yellow fever virus. Partial nucleotide sequence of parts of prM/E and the non-structural (NS) 5 genes and 3' non-coding region (3' NCR) was employed to characterize the origin of yellow fever virus (YFV) involved in both cases. Wild-type YFV was identified as the etiologic agent responsible for the disease.     

Management and control of yellow fever virus: Brazilian outbreak January-April, 2018

ABSTRACT

Yellow fever virus (YFV) has a long history of causing human disease. Today, YFV is persevered in jungle environments with occasional sporadic human outbreaks in South America and periodic intermediate human transmissions with occasional urban outbreaks in sub-Saharan Africa. The ever-present risk of outbreak is primarily controlled for via vaccination coverage to vulnerable human populations. Global vaccine supplies have been strained in the setting of recent outbreaks in Africa and Brazil. The increasingly global community of today has placed an ever-growing tension on the management and control of YFV. A historic outbreak of YFV in Brazil is tracked from January to April 2018 using the International Society for Infectious Diseases’ (ISID) Program for Monitoring Emerging Diseases (ProMed). A narrative summary is generated from the review of 29 ProMed reports pertaining to the key words yellow fever and Brazil. Significant topics addressed include urban proximity, vaccination dose sparing with 1/5th standard dose, international travellers, epizootic trends, vaccine hesitancy, and mass immunisation campaigns. These topics are reviewed in detail for the current outbreak in comparison to previous outbreaks. Through close attention to these topics the degree and extent of the current outbreak was attenuated.     

Enzootic Transmission of Yellow Fever Virus,Venezuela

Phylogenetic analysis of yellow fever virus (YFV) strains isolated from Venezuela strongly supports YFV maintenance in situ in Venezuela, with evidence of regionally independent evolution within the country. However, there is considerable YFV movement from Brazil to Venezuela and between Trinidad and Venezuela.     

West Nile virus infection in nonhuman primate breeding colony, concurrent with human epidemic, southern Louisiana

During the summer of 2002, an epidemic of West Nile meningoencephalitis occurred in southern Louisiana. Following the outbreak, blood samples were collected from 1,692 captive rhesus monkeys (Macaca mulatta), pigtail macaques (M. nemestrina), and baboons (Papio spp.) that were permanently housed outdoors at a nonhuman primate breeding facility in St. Tammany Parish, Louisiana. The serum samples were examined for antibodies to West Nile virus (WNV). Overall, 36% of the captive nonhuman primates had WNV antibodies; comparison of these samples with banked serum samples from previous blood collections indicated that the animals were infected subclinically from February to August 2002. WNV activity was demonstrated in surveillance at the nonhuman primate-breeding colony and in the neighboring community during this same period. The high infection rate in this captive nonhuman primate population illustrates the intensity of WNV transmission that can occur silently in nature among other susceptible vertebrates during epidemic periods.     

Aedes aegypti in Brazil: genetically differentiated populations with high susceptibility to dengue and yellow fever viruses

Aedes aegypti was eliminated from Brazil in 1955, but re-infested the country in the 1970s. Dengue outbreaks have occurred since 1981 and became endemic in several cities in Brazil after 1986. Urban yellow fever has not occurred since 1942, and only jungle yellow fever cases have been reported. A population genetic analysis using isoenzyme variation combined with an evaluation of susceptibility to both yellow fever and dengue 2 viruses was conducted among 23 A. aegypti samples from 13 Brazilian states. We demonstrated that experimental infection rates of A. aegypti for both dengue and yellow fever viruses (YFV) are high and heterogeneous, and samples collected in the endemic and transition areas of sylvatic yellow fever were highly susceptible to yellow fever virus. Boa Vista, a border city between Brazil and Venezuela, and Rio de Janeiro in the Southeast region are considered as the most important entry points for dengue dissemination. Considering the high densities of A. aegypti, and its high susceptibility to dengue and yellow fever viruses, the risk of dengue epidemics and yellow fever urbanization in Brazil is more real than ever.     

Spatial distribution of arboviral mosquito vectors (Diptera, Culicidae) in Vale do Ribeira in the South-eastern Brazilian Atlantic Forest

Mosquitoes are vectors of arboviruses that can cause encephalitis and hemorrhagic fevers in humans. Aedes serratus (Theobald), Aedes scapularis (Rondani) and Psorophora ferox (Von Humboldt) are potential vectors of arboviruses and are abundant in Vale do Ribeira, located in the Atlantic Forest in the southeast of the State of S?o Paulo, Brazil. The objective of this study was to predict the spatial distribution of these mosquitoes and estimate the risk of human exposure to mosquito bites. Results of the analyses show that humans are highly exposed to bites in the municipalities of Cananéia, Iguape and Ilha Comprida. In these localities the incidence of Rocio encephalitis was 2% in the 1970s. Furthermore, Ae. serratus, a recently implicated vector of yellow fever virus in the State of Rio Grande do Sul, should be a target for the entomological surveillance in the southeastern Atlantic Forest. Considering the continental dimensions of Brazil and the inherent difficulties in sampling its vast area, the habitat suitability method used in the study can be an important tool for predicting the distribution of vectors of pathogens.     

Enzootic transmission of yellow fever virus in Peru

The prevailing paradigm of yellow fever virus (YFV) ecology in South America is that of wandering epizootics. The virus is believed to move from place to place in epizootic waves involving monkeys and mosquitoes, rather than persistently circulating within particular locales. After a large outbreak of YFV illness in Peru in 1995, we used phylogenetic analyses of virus isolates to reexamine the hypothesis of virus movement. We sequenced a 670-nucleotide fragment of the prM/E gene region from 25 Peruvian YFV samples collected from 1977 to 1999, and delineated six clades representing the states (Departments) of Puno, Pasco, Junin, Ayacucho, San Martin/Huanuco, and Cusco. The concurrent appearance of at least four variants during the 1995 epidemic and the genetic stability of separate virus lineages over time indicate that Peruvian YFV is locally maintained and circulates continuously in discrete foci of enzootic transmission.     

Rift Valley Fever Outbreak,Southern Mauritania, 2012

After a period of heavy rainfall, an outbreak of Rift Valley fever occurred in southern Mauritania during September–November 2012. A total of 41 human cases were confirmed, including 13 deaths, and 12 Rift Valley fever virus strains were isolated. Moudjeria and Temchecket Departments were the most affected areas.     

Arbovirus prevalence in mosquitoes, Kenya

Few studies have investigated the many mosquito species that harbor arboviruses in Kenya. During the 2006-2007 Rift Valley fever outbreak in North Eastern Province, Kenya, exophilic mosquitoes were collected from homesteads within 2 affected areas: Gumarey (rural) and Sogan-Godud (urban). Mosquitoes (n = 920) were pooled by trap location and tested for Rift Valley fever virus and West Nile virus. The most common mosquitoes trapped belonged to the genus Culex (75%). Of 105 mosquito pools tested, 22% were positive for Rift Valley fever virus, 18% were positive for West Nile virus, and 3% were positive for both. Estimated mosquito minimum infection rates did not differ between locations. Our data demonstrate the local abundance of mosquitoes that could propagate arboviral infections in Kenya and the high prevalence of vector arbovirus positivity during a Rift Valley fever outbreak.     

Passatempo virus, a vaccinia virus strain, Brazil

Passatempo virus was isolated during a zoonotic outbreak. Biologic features and molecular characterization of hemagglutinin, thymidine kinase, and vaccinia growth factor genes suggested a vaccinia virus infection, which strengthens the idea of the reemergence and circulation of vaccinia virus in Brazil. Molecular polymorphisms indicated that Passatempo virus is a different isolate.     

中缅边境地区孟连和澜沧县登革热媒介蚊虫调查

目的了解中缅边境地区孟连和澜沧县登革热媒介种类、生态习性和登革热病毒自然感染状况,为登革热预防控制提供科学依据。方法在孟连和澜沧县选择3个自然村作为监测点,采用人工诱捕法白天诱捕成蚊,并在房屋内外积水容器捕捞幼虫,采用RTPCR方法对现场捕获的成蚊进行登革热病毒检测。结果 2010年6-10月在孟连和澜沧县监测点共捕获蚊虫6属8亚属22种3436只,其中白纹伊蚊为优势蚊种,占捕蚊总数的33.82%;未捕到埃及伊蚊。3个观察点白纹伊蚊平均房屋指数19.3,容器指数5.84,布雷图指数30.3,千人指数68.5;白纹伊蚊孳生环境类型以竹筒、土罐类和旧轮胎等临时积水容器为主,分别占阳性积水容器数的34.1%、27.5%和17.6%;白纹伊蚊成蚊平均密度为8.98只/人工小时;成蚊密度高峰出现在7-8月;对捕获的29批白纹伊蚊(1162只)进行RTPCR检测,未发现登革热病毒感染。结论白纹伊蚊密度较高且分布广泛,应加强当地登革热监测工作。     

Urban yellow fever epidemic in western Nigeria, 1987

A large epidemic of urban yellow fever occurred in April and May 1987 in Oyo State, western Nigeria. The principal vector was Aedes aegypti, breeding in domestic water containers. The 1987 outbreak followed an epidemic of sylvatic yellow fever in eastern Nigeria the previous year, and probably resulted from introduction of the virus by viraemic travellers. The outbreak in Oyo State ended in early July, by which time 805 cases and 416 deaths had been officially notified. However, surveys of 3 villages in the epicentre, a region with over 4 million inhabitants, indicated an infection rate of approximately 20%, a clinical attack rate of 2.9% and a mortality rate of 0.6%, suggesting that the true incidence of cases and deaths far exceeded the official reports. Yellow fever virus was isolated from persons with fully developed yellow fever as well as mild febrile illness. One virus isolate was made from blood of an individual with mild illness, who had received 17D vaccine 5 d earlier; monoclonal antibody analysis showed that the isolate was a wild-type virus. Larval indices of Ae. aegypti were very high; however, low vector competence of the Ae aegypti population may have provided a constraint on spread of the epidemic. In late 1987 a third epidemic appeared in Niger State, northern Nigeria, with 644 reported cases and 149 deaths. The vector(s) involved is (are) unknown.     

Reemergence of Rift Valley Fever,Mauritania, 2010

A Rift Valley fever (RVF) outbreak in humans and animals occurred in Mauritania in 2010. Thirty cases of RVF in humans and 3 deaths were identified. RVFV isolates were recovered from humans, camels, sheep, goats, and Culex antennatus mosquitoes. Phylogenetic analysis of isolates indicated a virus origin from western Africa.     

Yellow fever virus infectivity for Bolivian Aedes aegypti mosquitoes

The absence of urban yellow fever virus (YFV) in Bolivian cities has been attributed to the lack of competent urban mosquito vectors. Experiments with Aedes aegypti from Santa Cruz, Bolivia, demonstrated infection (100%), dissemination (20%), and transmission of a Bolivian YFV strain (CENETROP-322).     

Rift Valley fever outbreak--Kenya, November 2006-January 2007

In mid-December 2006, several unexplained fatalities associated with fever and generalized bleeding were reported to the Kenya Ministry of Health (KMOH) from Garissa District in North Eastern Province (NEP). By December 20, a total of 11 deaths had been reported. Of serum samples collected from the first 19 patients, Rift Valley fever (RVF) virus RNA or immunoglobulin M (IgM) antibodies against RVF virus were found in samples from 10 patients; all serum specimens were negative for yellow fever, Ebola, Crimean-Congo hemorrhagic fever, and dengue viruses. The outbreak was confirmed by isolation of RVF virus from six of the specimens. Humans can be infected with RVF virus from bites of mosquitoes or other arthropod vectors that have fed on animals infected with RVF virus, or through contact with viremic animals, particularly livestock. Reports of livestock deaths and unexplained animal abortions in NEP provided further evidence of an RVF outbreak. On December 20, an investigation was launched by KMOH, the Kenya Field Epidemiology and Laboratory Training Program (FELTP), the Kenya Medical Research Institute (KEMRI), the Walter Reed Project of the U.S. Army Medical Research Unit, CDC-Kenya's Global Disease Detection Center, and other partners, including the World Health Organization (WHO) and Médecins Sans Frontières (MSF). This report describes the findings from that initial investigation and the control measures taken in response to the RVF outbreak, which spread to multiple additional provinces and districts, resulting in 404 cases with 118 deaths as of January 25, 2007.     

Absence of YF-neutralizing antibodies in vulnerable populations of Brazil: A warning for epidemiological surveillance and the potential risks for future outbreaks

Yellow Fever (YF) is an acute febrile illness caused by yellow fever virus (YFV), a mosquito-borne flavivirus transmitted to humans and non-human primates. In Brazil, YF is a public health threat and may cause recurrent epidemics, even with the availability of a vaccine. We evaluated the sero-status for YFV in 581 individuals living in a risk area for YF in Brazil. The area presents history of cases and is located in the southeast region of country where outbreaks of YF have been reported since 2016. Through, a PRNT assay, we found 25.8% of individuals lacking YF-neutralizing antibodies. Furthermore, neutralizing antibodies were not detected in 10 individuals with proven vaccination. Our findings reinforce the importance of surveillance systems and the need of an urgent intensification of immunization programs in regions with YFV circulation. Monitoring susceptible individuals that could act as potential disseminators for YFV in risk areas should also be considered.     

Citywide Integrated Aedes aegypti Mosquito Surveillance as Early Warning System for Arbovirus Transmission,Brazil

Arbovirus epidemiology lacks efficient and timely surveillance systems with accurate outbreak alert signals. We devised a citywide integrated surveillance system combining entomologic, epidemiologic, and entomo-virologic data gathered during 2017–2020 in Foz do Iguaçu, Brazil. We installed 3,476 adult mosquito traps across the city and inspected traps every 2 months. We compared 5 entomologic indices: traditional house and Breteau indices for larval surveys and trap positivity, adult density, and mosquitoes per inhabitant indices for adult trapping. We screened for dengue, Zika, and chikungunya viruses in live adult Aedes aegypti mosquitoes collected from traps. Indices based on adult mosquito sampling had higher outbreak predictive values than larval indices, and we were able to build choropleth maps of infestation levels <36 h after each round of trap inspection. Locating naturally infected vectors provides a timely support tool for local public health managers to prioritize areas for intervention response to prevent virus outbreaks.     

Entomological investigation of a sylvatic yellow fever area in São Paulo State, Brazil

Following reports of two autochthonous cases of sylvatic yellow fever in the State of S?o Paulo, Brazil, in 2000, entomological surveys were conducted with the objective of verifying the occurrence of vector species in forest environments close to or associated with riparian areas located in the western and northwestern regions of the State. Culicidae were captured in 39 sites distributed in four regions. Haemagogus leucocelaenus and Aedes albopictus were the most abundant species and were captured in all the regions studied. H. leucocelaenus was the most abundant species in the municipalities of Santa Albertina and Ouroeste, where the two cases of sylvatic yellow fever had been reported. Mosquitoes from the janthinomys/capricornii group were only found at eight sites in the S?o José do Rio Preto region, while Sabethes chloropterus was found at one site in Ribeir?o Preto. H. leucocelaenus showed its capacity to adapt to a secondary and degraded environment. Our results indicate a wide receptive area for yellow fever transmission in the State of S?o Paulo, with particular emphasis on the possibility of H. leucocelaenus being involved in the maintenance of this sylvatic focus of the disease.     

Waterborne toxoplasmosis, Brazil, from field to gene

Water was the suspected vehicle of Toxoplasma gondii dissemination in a toxoplasmosis outbreak in Brazil. A case-control study and geographic mapping of cases were performed. T. gondii was isolated directly from the implicated water and genotyped as SAG 2 type I.