A new study identifies several regions around the world with the highest number of unknown viruses likely to infect people, and which species are most likely to carry them.
Researchers from New York-based environmental non-profit EcoHealth Alliance published a study Wednesday in the journal Nature they say is the first comprehensive analysis of all viruses known to infect mammals.
The world has seen a rise in the number of zoonotic viruses, or viruses that can be transmitted from animals to humans. The goal of the study is to try to predict where the next pandemic is likely to occur, and which species are most likely to carry it, said the study's senior author, Peter Daszak, who is president of EcoHealth Alliance.
"If you are an organization that is doing surveillance to stop the next Ebola — and we know there are a hundred other Ebola viruses we have not discovered out there on the planet — this paper says where they would be," Daszak said. "And then you can target your programs to go an look for them. And if you find them you can determine whether it is likely something that can infect people.
Geographically, the biggest hotspots are the tropical regions of the world, such as Central and South America, West and Central Africa, and Southeast Asia.
Apart from being some of the most biodiverse places on the planet, they are also the regions that are home to the greatest number of species that have the highest risk of carrying and transmitting viruses to humans.
One of the most striking findings is that bats carry a significantly higher proportion of zoonotic diseases than any other group of mammals.
This finding contradicted what Daszak had thought for years.
"It's kind of funny," Daszak said. "We have been debating this for years and I have been saying there is no evidence that bats carry more diseases." But the study proved him wrong.
Bats carry Middle East Respiratory Syndrome, Severe Acute Respiratory Syndrome, the Ebola virus and many others. But scientists still don't know what makes them so extraordinary in this respect, he said.
It might be that bats live in such large colonies, and develop special immunities to disease. They are also closely related to humans, which might explain why they can transmit diseases so easily to humans.They are the only flying mammal, so they might have had to pay some evolutionary price for flight, such as having a weaker lymph system, Daszak said. It might be that they are migratory, and therefore likely to pick up more diseases.
This means that regions where bats live — particularly South and Central America and parts of Asia — are places that could have a high number of potentially harmful viruses that have not been discovered yet.
Primate species, such as monkeys and apes, were tied with rodents for being the second most prevalent carriers of zoonotic diseases.
"If you wanted to predict the next pandemic, you could study just bats, primates and rodents and cover a lot of the risk," Daszak said.
But one of the most important points of the study, Daszak said, is that humans place themselves at risk for these diseases when they venture into the regions where these species live.
Daszak said the wildlife trade, bush meat hunting — such as bat hunting in Southeast Asia —deforestation and development of the rainforest are all bringing humans into contact with these animals.
"If we don't build the road into the forest, or go in there hunting bush meat, we aren't going to catch the viruses," he said. "They simply won't have the opportunity to get into people."