Night began to fall in Rio de Janeiro's Pedra Branca state park as four Brazilian scientists switched on their flashlights to traipse along a narrow trail of mud through dense rainforest. The researchers were on a mission: capture bats and help prevent the next global pandemic. A few meters ahead, nearly invisible in the darkness, a bat made high-pitched squeaks as it strained its wings against the thin nylon net that had ensnared it.
One of the researchers removed the bat, which used its pointed teeth to bite her gloved fingers. The November nighttime outing was part of a project at Brazil's state-run Fiocruz Institute to collect and study viruses present in wild animals including bats, which many scientists believe were linked to the outbreak of COVID-19.
The goal now is to identify other viruses that may be highly contagious and lethal in humans, and to use that information to devise plans to stop them from ever infecting people to forestall the next potential global disease outbreak before it gets started. In a highly connected world, an outbreak in one place endangers the entire globe, just as the coronavirus did. And the Brazilian team is just one among many worldwide racing to minimise the risk of a second pandemic this century.
It's no coincidence that many disease scientists are focusing attention on bats, the the world's only flying mammals. Bats are thought to be the original or intermediary hosts for multiple viruses that have spawned recent epidemics, including SARS, MERS, Ebola, Nipah virus, Hendra virus and Marburg virus. A 2019 study found that of viruses originating from the five most common mammalian sources primates, rodents, carnivores, ungulates and bats those from bats are the most virulent in humans.
Bats are a diverse group, with more than 1,400 species flitting across every continent except Antarctica. But what many have in common are adaptations that allow them to carry viruses that are deadly in humans and livestock while exhibiting minimal symptoms themselves meaning they are able travel and shed those viruses, instead of being quickly hobbled. The secret is that bats have unusual immune systems, and that's related to their ability to fly, said Raina Plowright, an epidemiologist who studies bats at Montana State University.
Plowright and other bat scientists believe evolutionary tweaks that help bats recover from the stress of flying, when their metabolic rate rises sixteen-fold, also give them extra protection against pathogens. Probing the secrets of bat immune systems may help scientists understand more about when bats do shed viruses, as well as providing hints for possible future medical treatment strategies, said Arinjay Banerjee, a virologist at McMaster University in Canada.
Increasing destruction and fragmentation of habitats worldwide especially biodiverse areas like tropical forests means we are seeing higher rates of contact between wildlife and humans, creating more opportunities for spillover, said Cara Brook, a disease ecologist at the University of California, Berkeley.
