Preventing future pandemics starts with recognizing links between human and animal health.
The COVID-19 pandemic has demonstrated that zoonotic diseases – infections that pass from animals to humans – can present tremendous threats to global health. More than 70% of emerging and reemerging pathogens originate from animals. That probably includes the SARS CoV-2 virus, which scientists widely believe originated in bats.
There are still questions about specifically where the SARS-CoV-2 virus emerged. But experts across the globe agree that communities can take steps to reduce the risk of future spillovers. A key is for veterinarians, doctors and scientists to work together, recognizing how closely connected human health is with that of animals and of the habitats that we share – an approach known as One Health.
To prevent new pandemics, scientists need to identify specific locations where viruses are most likely to make the jump from animals to humans. In turn, this requires understanding how human behaviors – from deforestation to fossil fuel combustion to conflict to cultural activities – contribute to spillover risks.
How can nations prevent more pandemics like COVID-19? One priority is reducing the risk of diseases’ jumping from animals to humans. And that means understanding how human actions fuel that risk.
Recognizing risky zones
Identifying high-risk areas for zoonotic spillover is challenging. People and wildlife move around a lot, and exposure may not lead immediately to infection or produce symptoms that clearly reflect exposure to pathogens.
But researchers can make predictions by combining data on human and livestock density with that on environmental conditions, such as deforestation and land use changes, that can enable pathogens to spread from wildlife to humans. For instance, there are areas in China, Indonesia, India and Bangladesh where development has fragmented forests and extended animal farming and human communities near the natural habitats of horseshoe bats. This group of bats, which includes more than 100 species, has been implicated as a reservoir for many coronaviruses.
It’s not uncommon for bat-borne diseases to spill over to humans. Sometimes it happens directly: For example, bats in Bangladesh have repeatedly transmitted Nipah virus to humans. Or the pathogen can move indirectly via intermediate hosts. For example, in 1994 bats in Australia infected horses with Hendra virus, a respiratory disease that then passed to humans.
In Brazil, yellow fever is endemic in the jungles, spread mainly between monkeys via mosquitoes. People in the country occasionally contract it from mosquito bites, and deforestation and land conversion for farming are increasing the risk of greater spillovers. There is rising concern that the disease could be introduced into Brazil’s large cities, where Aedes aegypti mosquitoes are widespread and could transmit it on a large scale.
In our view, it is essential for researchers and governments to understand and embrace the central concept that the health of animals, people and the environment is closely connected, and factors that affect one can affect all. Ideally, problem-solving teams form that address prevention from the community and district levels to the ranks of health, animal and environmental ministries.
Members of local communities are most likely to know where people run the highest risk of coming in contact with animals that may carry infectious diseases. By listening to them, veterinary and medical health professionals, as well as foresters and land managers, can develop strategies that are more likely to decrease the risk of spillover.