Photos: Reuters / Photoillustration by Jaclyn LoRaso
By Erika Fry
August 22, 2014

He was that passenger—an elderly gentleman in the back row, hacking away as the plane hurtled over Europe. And whatever he had, certainly the 30 other passengers, breathing the same stale cabin air for the duration of the seven-hour, cross-continental flight, would be at risk of having soon.

This was early May and the plane was bound for Amsterdam, carrying a tour group of Muslim pilgrims who had spent the previous three weeks in Saudi Arabia, performing the Umrah, a sacred pilgrimage, to the Islamic holy cities of Mecca and Medina. As part of their trip, the passengers had visited mosques, completed the attendant rituals, and gone to local markets and eateries. Some in the group had also traveled to Medina’s outskirts, where they encountered a herd of dromedary camels and drank raw camel’s milk with a group of farmers.

By the time the group landed in the Netherlands, the old man with the cough was in terrible shape—short of breath with a mild fever of 38.2-degree Celsius (just under 101 degrees Fahrenheit). He was taken to the hospital where, three days later, after a barrage of medical tests and thorough examination, he was pronounced the Netherlands’ first case of Middle East respiratory syndrome (MERS). The next day, his sister, his seatmate on the flight and roommate for the trip, became the second.

The elderly passengers are the very sort that animate public health drills and the plots of scary pandemic movies: carriers of a mysterious, little-understood infectious disease, who board an international flight—the most ready and perfect of incubation chambers—and then bring it home. Disease could not dream of better conditions to flourish. Witness this striking 2012 animation by researchers in MIT’s Department of Civil and Environmental Engineering, who used network theory and other scientific tools to predict the roles that 40 major U.S. airports would play in the spread of a new infectious disease.


And yet, when MERS was given the chance, it didn’t make it beyond the already-infected siblings in the aircraft’s back row. None of their fellow passengers have gotten the frightening respiratory syndrome. The episode—similar to those involving individuals who have imported MERS to other countries, including the U.S.—is a telling one about how the virus spreads among humans: not so easily.

As part of a Fortune series on contagion, I examined how the deadly MERS coronavirus is thought to have traveled from animals to humans; for this second story in the series, I set out to track how it has (and hasn’t spread) among humans. By studying the strange and unpredictable way things spread—in other essays, my colleagues report on the seeming domino effects inherent in M&A rumors, market panics, and even the popularity of a dense economics treatise—we hope to get closer to understanding the science, or at least the patterns, behind contagion.

As with the case of MERS traveling from animals to human beings, epidemiologists are still trying to figure out precisely how MERS is transmitted from one human being to another. Particularly mysterious are a number of MERS patients who have reported no recent contact with animals or other infected individuals. Based on cases on the disease that are best understood, it would appear that MERS is not as readily airborne as the SARS virus, but rather spreads (at least for now) only through “droplet” transmission. As a respiratory virus, particles of MERS-CoV travel via droplets of respiratory secretions such as coughs, sneezes and spit. Those particles either land directly on a person or settle on a surface where they are later swiped up by someone. That person then becomes infected when they rub their eyes, touch their mouth or otherwise introduce the virus into their system. The incubation period for MERS is 2-14 days.

The elderly pilgrim, in all likelihood, didn’t get MERS from drinking raw camel’s milk. He was not among the group that encountered the herd of dromedaries; instead he had his own local adventure—he had visited four hospitals in the country. At the first two, in Medina, he had sat in waiting rooms, as his adult son saw a doctor for an unrelated medical issue. And at the second two, in Mecca, the man had been a patient himself, suffering from fatigue, fever and diarrhea. His sister developed similar symptoms several days later but she did not visit a hospital.

The old man probably picked up his case of MERS at a Saudi hospital, which is the one place where the coronavirus has truly thrived and where outbreaks have developed when MERS patients have infected healthcare workers who in turn have infected other patients, who may be particularly vulnerable because of weakened immune systems. (Both of the elderly siblings suffered from diabetes and cardiovascular problems that made them particularly susceptible to infection.)

Such an outbreak occurred in the spring of 2013 in Al-Ahsa, a city in eastern Saudi Arabia, when the virus spread to 23 people who had circulated through the city’s hospital, particularly its intensive-care and dialysis units. And this spring, MERS cases in Saudi Arabia spiked again, due to a hospital outbreak in Jeddah. The increase in cases was so startling that many feared the virus had mutated into a more virulent form; the World Health Organization has since declared that the spike was not due to a sudden change in the virus, but rather to “suboptimal” disease-control standards in Saudi hospitals. (Some in the public health community believe “super-spreaders” played a role in these events, though others say that’s not clear).

This spring, two MERS cases turned up in the U.S.—the first, on April 28, in Munster, Ind., the second on May 9, in Orlando, Fla. Both patients were healthcare workers who had recently flown to the U.S.

Hospitals and healthcare workers have been key to the spread of virus before: with SARS many hospital workers became infected when they tried to insert breathing tubes in patients with the virus. (The tube insertion typically causes a lot of coughing.) Yet, this lesson was learned early, and SARS was contained in just 6 months.

That MERS continues to circulate two years after its first outbreak, and that much remains unanswered about the virus makes many in the medical community worry that they will get the answers too late. That’s a scary prospect, but also a frustrating one to scientists who say greater progress would have been made—and MERS infections prevented—had Saudi Arabia’s government been more willing to share information and involve the international community in handling its MERS outbreaks. Dr. Keiji Fukuda, the WHO’s Assistant Director-General, in June told the AP that “the vast majority” of hospital infections probably could have been prevented.

Even now, basic epidemiological steps have not been taken, says Dr. David Heymann, former executive director of communicable diseases at the WHO and now, head of global health security at Chatham House. “There’s not been a coordinated effort to understand the infection. It’s been piecemeal,” he told me earlier this summer, noting that a proper case-control study, which might identify patterns of exposure among patients, had not yet been completed.

“This should have been done as early as possible to prevent deaths,” says Heymann. “But because it hasn’t been done, people are getting infected and giving it to others through close contact.”

Practices at medical facilities in the Kingdom have also been criticized. On a mission to Saudi Arabia in May, the WHO found that the country’s hospitals were overcrowded and “standard infection control practices were suboptimal.”

This, too, is not that unusual with an infectious disease. Countries that find themselves at the origin of an outbreak usually try to manage the situation without the international community’s help—and often end up fostering the spread of disease.

Many say Saudi Arabia and other countries in the region have turned a corner. In recent months Saudi Arabia fired its health minister, and the Kingdom’s agricultural ministry—which oversees livestock and which, for a long time, stayed silent on the potential role of camels—has become active in efforts to manage the situation.

While such developments are encouraging, though, MERS continues to spread—and with each case, it has a chance to become more deadly.

In May, the same month that the elderly Umrah pilgrims flew home to the Netherlands with MERS, two pilgrims introduced the virus to Algeria. So did an Iranian pilgrim, who didn’t show signs of MERS, but who passed it on to two sisters in a Southeastern province of the country.

Of the 7 billion people on the planet, they seemed unlikely candidates to become MERS victims. They had no recent history of travel, nor any recent contact with animals. Even so, by early June, one of them was dead—a reminder of how cruel, random and undiscriminating, a virus can be.


For more inside the world of contagion, see

• CONTAGION—How things spread. Introducing a new Fortune series

• Part 1: How a bat virus became a human killer

• Part 2: How the MERS virus made it to Munster, Indiana

• Part 3: How M&A rumors spread

• Part 4: How market selloffs happen

• Part 5: How Americans fell in love with a 685-page economics treatise

• Part 6: How the “selfie” became a social epidemic

• Part 7: How studying Twitter became an academic craze


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