The nonprofit EcoHealth Alliance recently published the results of a multiyear study in the journal Nature on how pandemics originate and spread. The team observed that most of the deadly emerging infectious diseases originate with viruses in wild mammals, known as zoonotic viruses. This includes HIV, Ebola, and SARS. They studied which species carried the most zoonotic viruses, and what proportion of that population was likely to be infected.
The researchers found that bats carry a “significantly higher proportion of zoonotic viruses” than other mammals. On average, each species of bat harbored 17.2 viruses which could infect people, followed by primates at 9.7 and rodents at 9.6.
One goal of this research was to try and predict what the next deadly pandemic might be, and where it might break out. So far, 53 viruses from bats have infected people with diseases including Ebola, SARS, and MERS. With 1,200 species of bats around the world, there are thousands of more viruses that have yet to be discovered. Researchers identified the places where mammals, including bats, carry viruses and are increasingly encountering people, particularly: bats in the Amazon in Brazil, in part due to the logging business, and West Africa, where an increased agriculture results in contact with rodents. Rodents are also a concern in the Southwest U.S., and primates in Southeast Asia and Central Africa. The researchers have said that part of the problem is increased deforestation and development, as well as ‘bush meat hunting’, all of which increase the chances people will encounter the viruses.
No one is fully sure why bats carry so many viruses, but some theories argue that the cause might be that they live in large groups and are migratory animals, both of which may have effects on their immune system and how many diseases they encounter. Bats are also closely related to humans, so they may transmit diseases to humans easier than other species. The spread of pandemics among humans has been accelerating, for similar reasons: growing populations and urbanization, new environments, climate change, increased global travel, and civil conflict, among others. In 2016, pandemics cost more than $60 billion a year around the world but receive a fraction of the funding from major powers that other destabilizing security issues do. The U.S. budget has not yet been finalized, but it proposes major cuts to the NIH, which funds global health research and training, and may have a significant effect on world health and decrease global resistance to the spread of pandemics.
Sources and Further Reading:
Predicting the Next Pandemic – The Wall Street Journal
Health Experts Call for $4.5 Billion Annually to Fight Pandemics – The Wall Street Journal
Proposed NIH Budget Cuts Threaten Global Health Programs – Global Resilience Institute