Deadly MERS Mystery Maybe Solved: Bats One Up Camels

Even if we find the MERS virus living naturally in bats, we do not know how the bug gets into humans -- and luckily it's an extremely rare event.
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For over a year now, medical researchers have been searching for the source of the new coronavirus that has killed dozens of people that lived in, or traveled to, the Middle East. Viruses typically are named for where they are found, so this one has been dubbed the Middle East Respiratory Syndrome Coronavirus, or MERS-CoV for short. Earlier this month, a team of European researchers published findings in the prestigious medical journal The Lancet that suggested that camels both in Oman and, oddly, on the Spanish Canary Islands had been exposed to the virus that has been killing people, or a virus so similar that their tests were unable to distinguish the difference. In those tests, the disease-causing virus itself was not found, but the animals' immune system responses suggested exposure to MERS CoV or a very close cousin. This vagary is not unusual in the world of wildlife health. Frequently, we are faced with the unfortunate reality that blood tests may work well in one type of animal and poorly for thousands of others species. Camels too, have their peculiarities. Both their blood cells and their immune systems are unlike other animals.

Now, new evidence from Saudi Arabia, released this week ahead of print in the journal Emerging Infectious Diseases, may have lead us to the smoking gun, or at least a smoking gun part. The researchers, lead by the Kingdom's Deputy Minister of Health Dr. Ziad Memish, along with my colleagues from EcoHealth Alliance and Columbia University's Center for Infection and Immunity found a small gene fragment in the tiny droppings of a bat that is a perfect match with the same genetic sequence of MERS CoV. Of course, there are many other parts of the virus's genome, so this evidence is akin to a partial fingerprint. But, given what we know about the nature of these so-called new emerging diseases, a link between MERS CoV and bats make a lot of sense.

The majority of novel infectious diseases are linked to wildlife. As one of the new study's authors Dr. Peter Daszak of EcoHealth Alliance puts it, "Considering that a large percentage of the world's wild mammals are bats and that most have been poorly studied, it's predictable that we will continue to find new viruses in them."

In fact, a ground-breaking project supported by the U.S. Agency for International Development called PREDICT is doing exactly that. Dr. Jonna Mazet at the University of California -- Davis and director of the PREDICT project notes, "In just a few years of our studies in only 20 countries, we've already identified over 250 new viruses in wildlife and a large percentage of these are new coronaviruses from bats."

So, is the mystery solved? Actually, not quite. The medical world still expects proof that meets the criteria set forth by the two German scientists Robert Koch and Friedrich Loeffler in late 1800s. This requires finding the live, disease-causing microbe in an animal or human, then putting it in another to produce an infection and finally, obtaining the microbe again from the new victim. On a more practical note, even if we find the MERS virus living naturally in bats, we do not know how the bug gets into humans -- and luckily it's an extremely rare event. Are people touching, ingesting, or inhaling the virus excreted in bat feces? Are bats contaminating food items eaten by people, or objects like tools stored in a shed or barn where bats live? Or are camels, their hay or their tack being contaminated by bats, allowing the virus to infect people who work with them, ride them, eat them or milk them? Although we still don't know the answers to these questions, 3 to 6 million people from around the world will soon make the annual pilgrimage to Mecca this fall and my mother's guidance (also from Germany) may help: Wash your hands, don't rub your face, and cook your food.

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