Characterizing the transmission chains of zoonotic viruses between wildlife and humans: the case of Coronaviruses and Hantaviruses in the Yucatan Peninsula (Mexico)

The increasing frequency of zoonotic viruses highlights the crucial importance of characterizing the transmission chains of certain viruses of public health interest between wildlife communities and human populations. This project therefore aims to characterize each of these steps and to define how their interactions can impact the emergence of zoonoses. Bats are the natural reservoirs of many zoonotic viruses, but their role in environmental viral shedding remains poorly documented. However, environmental shedding of zoonotic viruses by bats can induce the infection of intermediate species, such as rodents, which share part of their environment with bats and humans, thus promoting viral exchanges. This project therefore seeks to determine whether rodents play a bridging role between wildlife and human populations in viral transmission. Specifically, the TRANSVI project will focus on the potential emergence of two RNA viruses, Coronaviruses and Hantaviruses, known to cause hemorrhagic fevers or respiratory viruses once adapted to humans. Focusing on vulnerable human populations in the Yucatan Peninsula (Mexico), a region recognized as one of the potential hotspots for the emergence of zoonoses, the first part of the project aims to identify Coronaviruses and Hantaviruses circulating between bats and rodents by assessing the presence of similar viral strains in bat feces (guano), as well as in blood samples from bats and rodents. This work will make it possible to make an inventory of the targeted viruses circulating in bat and rodent populations, but also to determine the impact of environmental viral excretion through feces on rodent exposure. The second Work Package will assess the role of bats and rodents in human exposure to the same viruses. This component will statistically analyze the link between human exposure, obtained from an ongoing serological study conducted in villages near the animal sampling sites, and the circulation of these viruses in bats and rodents. This analysis will also integrate the factors promoting contact between human populations and bat/rodent communities (outdoor activities, consumption of bat meat, etc.) identified during a socio-epidemiological study in order to identify transmission routes. Over the last three years, intensive sampling of bat and rodent species has been carried out at 3 sites in the Yucatan Peninsula, all close to vulnerable human populations. Blood samples from bats and rodents at these sites are already available and collection will continue from 2025 to 2027. External projects will fund serum collection from 3 human populations near the bat/rodent collection sites. TRANSVI will fund the collection and analysis of bat feces collected in the field, as well as the analysis of blood samples already obtained (PCR and sequencing). The project will also support serological analysis of human serum samples (Luminex), as well as the collection of socio-epidemiological data to identify exposure factors within human communities. In conclusion, this project proposes a comprehensive and innovative approach to better understand, prevent and control future zoonoses by characterizing each step of the viral transmission chain in an environment conducive to the development of new potential pandemics. In the medium term, this project will identify the species of bats and rodents to target in order to strengthen surveillance systems, but also improve the development of prevention strategies to limit transmission to human populations.