Mammals could harbour over 300,000 unknown viruses, says study

HIV, West Nile, SARS, Ebola, bird flu, and most recently MERS — viruses that make the jump from animals to humans are often only detected after they've made the jump and there's the mad scramble to identify it and find a treatment to save lives. However, a new study has given us the first look at just how many viruses we're up against, and has started researchers on the path to new methods that could help prevent epidemics before they happen.

"Historically, our whole approach to discovery has been altogether too random," says Simon Anthony, a scientist at Columbia University's Center for Infection and Immunity, according to a Columbia U statement. "What we currently know about viruses is very much biased towards those that have already spilled over into humans or animals and emerged as diseases. But the pool of all viruses in wildlife, including many potential threats to humans, is actually much deeper."

To get an estimate of just what we're up against, Anthony, Daszak, and their team looked at how many viruses could be found in just one animal — the Indian flying fox, which is apparently the largest flying mammal on the planet. These bats have been identified as the source of several outbreaks of the Nipah virus, which causes respiratory problems and inflammation of the brain that can result in death.

Specifically working with the bats found in Bangladesh (they range all over the Indian subcontinent), they found them carrying 55 viruses, only 5 of which were previously known. Allowing for there to be cases of more rare viruses that weren't found in the specific animals they examined, they used statistical methods to bump their estimate to an average of 58 viruses per species. Then, taking into account that there's nearly 5,500 known mammal species, that gave them a total estimate of around 320,000 viruses that could potentially affect us in the future.

"For decades, we've faced the threat of future pandemics without knowing how many viruses are lurking in the environment, in wildlife, waiting to emerge. Finally we have a breakthrough — there aren't millions of unknown [viruses], just a few hundred thousand, and given the technology we have it's possible that in my lifetime, we'll know the identity of every unknown virus on the planet," said Peter Daszak, the corresponding author of the study and president of EcoHealth Alliance, according to the Columbia U statement.

This estimate is just the beginning, and the real number could end up being higher (depending on whether the Indian flying fox has a fairly typical 'viral capacity' or not), but the study has already reaped some immediate benefits.

After identifying one new virus (called GBV-D) that's related to the viruses that cause hepatitis, the researchers are now surveying the people in the area for those who are suffering from hepatitis-like symptoms, to see if they are actually suffering from a GBV-D infection.

"I think in 20 years, this will be standard operating procedure," Daszak told The Scientist.

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What's the cost of detecting all these viruses?

The estimate for that is roughly $6.3 billion, if we try to go after all of them, including the rarest of them (and thus the most difficult). If we limit it to just the easier ones, the cost drops to $1.4 billion. Either way, that's a lot of money, but by comparison, the estimated cost of the SARS outbreak in 2003 on the global economy was around $40 billion (not to mention the lives of 775 people).

Given the concerns of just one of these viruses turning into a global pandemic that wipes us out (economically and biologically), the return on investment is quite high.

(Photo courtesy: Ian Waldie/Getty Images)

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