National Geographic News
Photo of hajj pilgrims walking.

Muslim pilgrims prepare to leave Mecca in October 2013. This year some pilgrims are wearing masks as a precaution against MERS, which has stricken hundreds of people, most in Saudi Arabia and the Middle East. The Saudi health minister said late Saturday that no cases have been detected among pilgrims.


Cynthia Gorney

for National Geographic

Published May 14, 2014

Epidemiologists are racing to understand and contain Middle East Respiratory Syndrome (MERS), the sometimes-lethal viral contagion spreading beyond its epicenter in Saudi Arabia. Many of them believe the MERS virus has proliferated in dromedary camels, and likely has its origins in bats.

This week, U.S. health officials disclosed that a second American had been diagnosed with MERS—the first, in April, was a Florida health care worker who had recently been in Saudi Arabia; the second, just announced Monday, is another Saudi Arabia-based health care worker who was visiting family in Florida. He was hospitalized May 8 in Orlando, and officials there said he remains in isolation and is improving.

For his recent book Spillover, National Geographic contributing writer David Quammen spent five years researching what he describes as an increasingly threatening form of infectious disease: zoonosis. That means human illness caused by viruses, bacteria, or other pathogens that have made the leap from animals to people.

Quammen recently answered some urgent questions raised by the MERS epidemic.

Why do some of these viruses become so destructive in human beings? Severe Acute Respiratory Syndrome, which killed nearly 800 people in 2003, was determined to be a virus "spillover" from bats to people. But the bats themselves didn't seem to be suffering from SARS or anything like it, right?

In a "reservoir host," like those bats, a virus can live harmlessly over the long term. It can replicate, but it doesn't cause cataclysmic disease. That's probably a result of a long association—in the case of bats, maybe a million years. But then it spills over into a new creature. It's got a new situation. And either it discovers this is a habitat in which it just can't live, or it's a habitat in which it can live but doesn't cause terrible disease.

Or, the third possibility—it discovers, "Wow! Here is a host in which I can thrive. I can replicate, I can cause all kinds of damage, and maybe I can even pass between one of these kinds of creatures and another"—one human and another. In that case, the virus has won the sweepstakes.

Photo of a man touching the mouth of a camel.
A man touches the lip of a young camel in the United Arab Emirates in December 2010. Scientists say camels in Saudi Arabia have been infected with MERS for at least two decades and that previous human cases were probably missed.
Photograph by Kamran Jebreili, AP

What sets off these spillovers—the initial spread from animal to person?

Opportunity. Some human comes into contact with an animal that's carrying a virus. It seems to be happening more in recent decades, probably for two reasons: First, we're better able to identify and track these diseases. Second, we're increasingly coming into contact with wildlife. More and more, we humans are going into tropical forests and the other really diverse ecosystems on the planet. We're cutting trees, killing animals, building timber camps, building mines, causing destruction—and we're offering the viruses that live in the wild animals of these places the opportunity to get into humans, and then pass from one human to another.

What exactly is a pandemic? Saudi and international health officials say MERS is not one—that this is what they are working so hard to avoid. What would have to happen—let us ardently hope it does not—for the "pandemic" label to be applied?

You have three categories. An outbreak is a localized event. An epidemic usually suggests something that has spread across a country. Apandemic is something that has spread quickly and broadly around the world. So far, there's only a sprinkling of MERS cases outside the Arabian Peninsula, and there are very careful public health steps being taken to control it.

This is a virus that bears very close watching, very rigorous measures to contain it. The greater the number of people it gets into, the greater the chance it can mutate into something new. That's why it's very important to control MERS at the beginning, so it doesn't have a chance to build up high levels of virus in a large number of people, giving it more chances to mutate. The current thinking among scientists and health officials seems to be that we should be highly wary—but not panicked.

For more on the spread of MERS, read Cynthia Gorney's National Geographic story Camels and Contagion: Inside Global Hunt for Source of MERS.

neil burman
neil burman

    As Matthew says, true Viruses dont respond to antibiotics. But the corona -  cold- viruses , like  herpes, HIV-AIDS, influenza, shingles, and bacteria like TB etc, certainly respond to vigorous dose and  blood level  eg for adults of  vitamin  C 3-10gms/d orally to tolerance (or intravenous); oral vitamin D3  80-100iu/kg/day to blood level  80->100+ ng/ml ; with the other immune-boosters eg iodine, zinc, vit A, selenium, (iron in the commonly deficient), N acetyl cysteine etc. . 

                                               In malnourished AIDS and TB sufferers, even modest doses of a combination of these supplements triple survival. It will be no different with MERS and the secondary bacterial infections that follow viral pneumonias..                               Cape Town

M. Öcal
M. Öcal

Humanity is to slaughter animals to hear that's the punishment from god

Matthew Rounseville
Matthew Rounseville

I think the biggest threat is if the MERS virus gets into one of the many refugee camps in the Middle East (Syria) and North Africa (Sudan). Under crowded conditions virus tend to become more virulent and spread more rapidly. The refugee camps will be like an incubator for a virus that is more adapted to infecting humans. The incubation period has been figured at 9-12 days; so by the time any refugees started showing symptoms, the virus will have been circulating in the population for a week or so. And UN workers, who deliver food and medicine and other supplies will have been traveling between camps and other major population centers. A pretty scary scenario since we have no vaccine and no effective antiviral drugs to treat patients. Careful monitoring and containing the virus is critical to avoid a potential pandemic.

p.s. Andrew, antibiotics as we commonly know them only work on bacteria, not on virus like the one that is causing MERS. And at this time we have no anti-viral drugs to treat infection by the MERS virus. But you're right about containment, that is our best method for preventing a larger outbreak or pandemic.

Andrew Schild
Andrew Schild

I think the CDC should seriously be looking after this disease and taking any and every precaution to prevent further outbreaks.  Since it is a virus, it will be most likely be treated with antibiotics, thus, giving it the opportunity to become immune to antibiotics.  People should avoid going to areas with recorded outbreaks. I am only 14, but this is my opinion.

David Seabaugh
David Seabaugh

The United States State Department should immediately ban all travel to and from the Middle East. This would protect Americans from MERS while providing countless beneficial, residual effects.

Sam Iam
Sam Iam

Avoid All Muslim Countries, But That Would Be Racist...

David Seabaugh
David Seabaugh

@Sam Iam. I know that you are being facetious, but FYI, it would literally be impossible to be "racist" against Muslims. Islam is a religion not a race. Ask Cat Stevens or John Walker Lindh or Mike Tyson or Kareem Abdul Jabar et al.


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