If this were an Indiana Jones movie, the plot would go something like this: a winged creature escapes from an ancient Egyptian tomb and unleashes a deadly evil across the land that leaves people sick and dying in its wake.
But when it comes to the Middle East respiratory syndrome, or MERS, fact might not be that far off from fiction – just subtract the supernatural stuff and throw in the findings from a new paper published today in Emerging Infectious Diseases.
The coronavirus that causes MERS has now sickened nearly 100 people and killed at least 46 but scientists are still scratching their heads over how it is infecting people. A crucial first step towards answering this mystery is finding the animal – or animals – harbouring the virus, which comes from the same viral family as SARS.
"We're really excited; it's a major breakthrough for us," says disease ecologist Dr. Peter Daszak, president of EcoHealth Alliance and one of the authors on the paper. "We've been looking at this for a year now and we've finally been able to get good evidence."
Most MERS cases have been in Saudi Arabia so the team traveled there last October and this past April, trapping 96 bats and collecting fecal samples from hundreds of others.
Only one bat had any trace of MERS, however – an Egyptian tomb bat from Bisha, the town where Saudi Arabia's first MERS victim lived and worked.
The scientists did not find live virus, nor did they find an entire coronavirus – just a snippet of one. Nonetheless, that viral fragment showed a 100 per cent genetic match for the MERS coronavirus found in the Bisha man who died in June 2012.
"The fact that it's just a snippet of the virus is frustrating but we're pretty confidant this is the reservoir," Daszak says. "It’s not just the fact that it’s 100 per cent (genetically matched), it’s also the fact that there are mechanisms for how the virus could get into people. These bats roost in abandoned buildings and in houses; they come close to humans."
The paper does not exclude the possibility that another animal could be acting as the intermediary between bats and humans; Lipkin and his team at Columbia are also now testing for MERS in 130 samples taken from Saudi Arabian livestock.
But Daszak has a hunch that the coronavirus is probably getting into people the same way something like Hantavirus does.
"You've got bat feces on the ground, it's dusty and you breathe it in," he says, noting that coronaviruses cause respiratory disease in humans. "It's the exact same mechanism that causes Hantavirus in humans."
Daszak believes it is important to find the animal host because then health authorities can take concrete steps to minimize contact between the MERS source and human populations. It can also help them identify those who are most at risk (for example, people who work in areas where these bats like to roost) and boost disease surveillance in other parts of the world where Egyptian tomb bats are known to live.
But Daszak thinks the discovery also underscores a bigger issue: that more and more wildlife viruses are now showing up in people, largely as a result of human activity bringing us into closer contact with new animals and pathogens.
"This isn’t all about bats carrying nasty viruses," he says. "The real issue is what we do in the environment that brings us into contact with these viruses. And if we can modify how we work in the environment – and be less intrusive and more clever about the way we develop agriculture and other things – we should be able to avoid these problems."