Yellow fever was the first human disease to receive an approved vaccine and has long been considered important to understanding how epidemics arise and should be controlled. Centuries after the disease was first reported in America, an international team of researchers will start a groundbreaking study to develop models that predict epidemics of yellow fever and other diseases caused by mosquito-borne arboviruses such as dengue, zika and chikungunya.
Knowledge of these diseases, their cycles, and the possibility of new outbreaks is very well known, but we still don’t have a systematic understanding of how to predict when outbreaks will occur. Our goal is to create predictive models to monitor and control outbreaks, protect the public, and develop a deeper understanding of the combination of factors that lead to epidemics.
Maurício Lacerda Nogueira, professor at the São José do Rio Preto (FAMERP) Faculty of Medicine in the Brazilian state of São Paulo and member of the CREATE-NEO project funded by the US National Institutes of Health (NIH).
The new study is part of a FAPESP-supported thematic project to monitor the mosquito population in the urban area of São José do Rio Preto and the monkey and mosquito populations in the transition zone between rural and urban Manaus, the capital of the Amazon.
The Brazilian research centers participating in the initiative include FAMERP, the National Institute for Amazon Research (INPA), the Mato Grosso Federal University (UFMT), the Amazonas Federal University (UF AM) and the Heitor Vieira Dourado Foundation for Tropical Medicine (FMT-HVD) ). Participants in other locations include the University of Texas Medical Department (UTMB), New Mexico State University (NMSU), Massachusetts Institute of Technology (MIT) and the Cary Institute of Ecosystem Studies in the United States, and the Gorgas Memorial Institute for Health Studies (ICGES) among others in Panama.
An article the researchers wrote to mark the start of the project is published in Emerging Topics in Life Science and examines the factors influencing the possible recurrence of yellow fever in neotropics.
The project also aims to find out more about spillovers and, if possible, anticipate those outbreaks where arboviruses jump from humans to animals or vice versa. Dengue, zika, and chikungunya are transmitted to humans and non-human primates by infected Aedes aegypti mosquitoes. In yellow fever, A. aegypti is the urban vector, but mosquitoes of a different genus (Haemagogus) are responsible for transmission in the countryside (Sylvatic Cycle).
Despite the existence of a highly effective vaccine since 1937 and since 1942 with no reported cases caused by urban transmission, sylvatic outbreaks of yellow fever to urban areas are common.
Many people and monkeys die from yellow fever in Brazil and other parts of America and Africa. Despite the vaccine and advances in controlling the transmission of the disease, we continue to see cases emerging from the Sylvatic cycle. The virus is endemic to part of Brazil, with an ongoing circulation between mosquitoes and non-human primates, which are its main hosts.
This enzootic cycle is far from easy to control.
Once established, the enzootic cycle ensures that the virus remains in forests or other rural areas, but can spread to a city by accidentally infecting a human. Therefore, it is important to conduct epidemiological surveillance studies and maintain large-scale vaccine supplies to control outbreaks.
Arbovirus predictive models also take into account climate change and urbanization that are destroying native vegetation.
We have active cases of yellow fever in both non-human primates and humans in the southern states of Paraná and Santa Catarina. This has not happened in several decades.
Maurício Lacerda Nogueira
The article “Recurrence of yellow fever in the Neotropic – quo vadis?” (doi: 10.1042 / ETLS20200187) by Livia Sacchetto, Betania P. Drumond, Barbara A. Han, Mauricio L. Nogueira and Nikos Vasilakis can be read at the following address: portlandpress.com/emergtoplifesci/article/4/4/411/227095 / Re-appearance-of-yellow-fever-in-the-neotropics-quo.
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