A review of emerging health threats from zoonotic New World mammarenaviruses.

Despite repeated spillover transmission and their potential to cause significant morbidity and mortality in human hosts, the New World mammarenaviruses remain largely understudied. These viruses are endemic to South America, with animal reservoir hosts covering large geographic areas and whose transmission ecology and spillover potential are driven in part by land use change and agriculture that put humans in regular contact with zoonotic hosts.We compiled published studies about Guanarito virus, Junin virus, Machupo virus, Chapare virus, Sabia virus, and Lymphocytic Choriomeningitis virus to review the state of knowledge about the viral hemorrhagic fevers caused by New World mammarenaviruses. We summarize what is known about rodent reservoirs, the conditions of spillover transmission for each of these pathogens, and the characteristics of human populations at greatest risk for hemorrhagic fever diseases. We also review the implications of repeated outbreaks and biosecurity concerns where these diseases are endemic, and steps that countries can take to strengthen surveillance and increase capacity of local healthcare systems. While there are unique risks posed by each of these six viruses, their ecological and epidemiological similarities suggest common steps to mitigate spillover transmission and better contain future outbreaks.

Understanding transmission risk and predicting environmental suitability for Mayaro Virus in Central and South America.

Mayaro virus (MAYV) is a mosquito-borne Alphavirus that is widespread in South America. MAYV infection often presents with non-specific febrile symptoms but may progress to debilitating chronic arthritis or arthralgia. Despite the pandemic threat of MAYV, its true distribution remains unknown. The objective of this study was to clarify the geographic distribution of MAYV using an established risk mapping framework. This consisted of generating evidence consensus scores for MAYV presence, modeling the potential distribution of MAYV in select countries across Central and South America, and estimating the population residing in areas suitable for MAYV transmission. We compiled a georeferenced compendium of MAYV occurrence in humans, animals, and arthropods. Based on an established evidence consensus framework, we integrated multiple information sources to assess the total evidence supporting ongoing transmission of MAYV within each country in our study region. We then developed high resolution maps of the disease's estimated distribution using a boosted regression tree approach. Models were developed using nine climatic and environmental covariates that are related to the MAYV transmission cycle. Using the output of our boosted regression tree models, we estimated the total population living in regions suitable for MAYV transmission. The evidence consensus scores revealed high or very high evidence of MAYV transmission in several countries including Brazil (especially the states of Mato Grosso and Goiás), Venezuela, Peru, Trinidad and Tobago, and French Guiana. According to the boosted regression tree models, a substantial region of South America is suitable for MAYV transmission, including north and central Brazil, French Guiana, and Suriname. Some regions (e.g., Guyana) with only moderate evidence of known transmission were identified as highly suitable for MAYV. We estimate that approximately 58.9 million people (95% CI: 21.4-100.4) in Central and South America live in areas that may be suitable for MAYV transmission, including 46.2 million people (95% CI: 17.6-68.9) in Brazil. Our results may assist in prioritizing high-risk areas for vector control, human disease surveillance and ecological studies.

Re-emergence of yellow fever in the neotropics - quo vadis?

Yellow fever virus (YFV) is the etiological agent of yellow fever (YF), an acute hemorrhagic vector-borne disease with a significant impact on public health, is endemic across tropical regions in Africa and South America. The virus is maintained in two ecologically and evolutionary distinct transmission cycles: an enzootic, sylvatic cycle, where the virus circulates between arboreal Aedes species mosquitoes and non-human primates, and a human or urban cycle, between humans and anthropophilic Aedes aegypti mosquitoes. While the urban transmission cycle has been eradicated by a highly efficacious licensed vaccine, the enzootic transmission cycle is not amenable to control interventions, leading to recurrent epizootics and spillover outbreaks into human populations. The nature of YF transmission dynamics is multifactorial and encompasses a complex system of biotic, abiotic, and anthropogenic factors rendering predictions of emergence highly speculative. The recent outbreaks in Africa and Brazil clearly remind us of the significant impact YF emergence events pose on human and animal health. The magnitude of the Brazilian outbreak and spillover in densely populated areas outside the recommended vaccination coverage areas raised the specter of human - to - human transmission and re-establishment of enzootic cycles outside the Amazon basin. Herein, we review the factors that influence the re-emergence potential of YFV in the neotropics and offer insights for a constellation of coordinated approaches to better predict and control future YF emergence events.

High mortality in aquatic predators of mosquito larvae caused by exposure to insect repellent.

In the face of mosquito-borne disease outbreaks, effective mosquito control is a primary goal for public health. Insect repellents, containing active compounds such as DEET and picaridin, are a first defence against biting insects. Owing to widespread use and incomplete sewage treatment, these compounds are frequently detected in surface waters, but their effects on aquatic taxa such as mosquito larvae or their naturally occurring aquatic predators are poorly understood. We investigated the effects of environmentally realistic concentrations of commercial products containing DEET and picaridin on survivorship of mosquito larvae, and their potential indirect effects on survival of larval salamanders, a major predator of mosquito larvae. Larval mosquitos were not affected by exposure to repellents containing DEET or picaridin. We found no larval salamander mortality in control and DEET treatments, but mortality rates in picaridin treatments ranged from 45 to 65% after 25 days of exposure. Salamander larvae exposed to repellents containing picaridin began to display tail deformities and impaired development four days after the experiment began. Our findings suggest the possibility that environmentally realistic concentrations of picaridin-containing repellents in surface waters may increase the abundance of adult mosquitos owing to decreased predation pressure.