Laurie Garrett and Maxine Builder / Foreign Policy

WASHINGTON — When the Black Death exploded in Arabia in the 14th century, killing an estimated third of the population, it spread across the Islamic world via infected religious pilgrims. Today, the Middle East is threatened with a new plague, one eponymously if not ominously named the Middle East respiratory syndrome (MERS-CoV, or MERS for short). This novel coronavirus was discovered in Jordan in March 2012, and as of June 26, there have been 77 laboratory-confirmed infections, 62 of which have been in Saudi Arabia; 34 of these Saudi patients have died.

Although the numbers — so far — are small, the disease is raising anxiety throughout the region. But officials in Saudi Arabia are particularly concerned.

This fall, millions of devout Muslims will descend upon Mecca, Medina and Saudi Arabia’s holy sites in one of the largest annual migrations in human history. In 2012, approximately 6 million pilgrims came through Saudi Arabia to perform the rituals associated with umrah, and this number is predicted to rise in 2013. Umrah literally means “to visit a populated place,” and it’s the very proximity that has health officials so worried.

In Mecca alone, millions of pilgrims will fulfill the religious obligation of circling the Kaaba. And having a large group of people together in a single, fairly confined space threatens to turn the holiest site in Islam into a massive petri dish.

The disease is still mysterious. Little is understood about how it is transmitted and even less regarding its origins. But we do know that MERS is deadly, with a mortality rate of about 55 percent — a remarkably higher lethality than that posed by its close cousin, the severe acute respiratory syndrome (SARS) virus, which in 2003 terrified travelers across the globe but posed a fatality rate of only 9.6 percent. The MERS coronavirus is new to our species, so mild and asymptomatic infections seem to be rare, but the human immune response to infection is itself so extreme that it can prove deadly in some cases.

Like SARS, the MERS virus spreads between people via close contact, shared medical instruments, and coughing. Once inside the human lung, the MERS virus sparks a series of reactions that all but destroy normal lung function. Patients can descend into pneumonia so severe that they require machine-assisted breathing to stay alive, in as little as 12 days. Unlike SARS, the MERS virus is also capable of attacking the kidneys and can be passed on to others via exposure to contaminated urine. And for some of those who survive acute MERS, years of rehabilitation may be necessary, just like for some of the 2003 SARS victims.

Pandemic risk

And like back in 2003, when health officials worried about airplane travelers in confined spaces transmitting the virus across the globe, the hajj poses a unique risk of transmission, one that could catapult this still-small outbreak into a full-fledged pandemic. Containment will become nearly impossible as millions of pilgrims flock from virtually every country on the globe to the kingdom during the holy month. Indeed, MERS has already crossed continents; two suspected cases were reported in France as recently as June 12, and confirmed cases have been reported in Germany and Britain. The first patient in each of these cases had traveled in the Middle East before reaching his or her home destination, only then to be diagnosed with MERS.

Traditionally, the onus to protect the pilgrimage and prevent disease rests on the shoulders of the Saudi royal family. Today, that responsibility lies with the kingdom’s Ministry of Health, which has deployed all its disease-fighting resources to tracking down MERS.

The ministry also must deal with the distinct possibility that pilgrims from abroad could bring other diseases to the kingdom, especially polio. (Saudi Arabia has been polio-free since 1995, but there was an importation as recently as 2004.) Polio is still endemic in several Muslim countries, including Nigeria and Pakistan, and outbreaks this year have surfaced in Somalia and Kenya. It has been eliminated in Saudi Arabia, but pilgrims from outside could carry the disease back into the region. Worryingly, live polio viruses identical to those circulating in Pakistan were discovered in the sewers of Cairo in January and in Israel in June.

Despite these risks of disease transmission, neither the World Health Organization nor the Saudi government has placed explicit travel guidelines in advance of this influx. In spite of having previously predicted that the number of pilgrims would increase from 2012, Saudi Arabia’s Ministry of Hajj has issued a directive to umrah visa operators to “cut down the number of foreign and domestic pilgrims by 20 and 50 percent, respectively,” reported a local newspaper that was quoting an informed source. In an unprecedented move, Saudi authorities are urging pilgrims to postpone their hajj plans due to “ongoing expansion work” at the Grand Mosque. Saudi clerics have also approved of this decision. It is unclear whether the timing of these announcements is mere coincidence or a discrete Saudi effort to limit the number of pilgrims without causing panic. Either way, cutting down on the number of pilgrims would be a fairly effective way to prevent the spread of MERS or any other virus.

Other potential carriers

But even if pilgrims postpone their plans for pilgrimage, they are not the only mobile population in the region who could serve as global vectors. As of April 2013, there were an estimated 7.5 million migrant workers living and legally working in Saudi Arabia; this number does not include the many more thousands of laborers in the country illegally. Migrant workers come from across the world, including India, Indonesia, Pakistan and the Philippines. According to a recent New York Times report, approximately 124,000 undocumented workers have left Saudi Arabia since April 1 under an amnesty program that lets them sort out their status without penalties for visa violations. The MERS outbreak also comes at a time when Saudi officials are looking to deport as many foreign workers as possible in order to free up the job market for Saudi nationals. This has caused tension — and in some cases violence — which increases distrust between the two groups and makes it less likely for an infected migrant worker to seek out medical care from, or to cooperate with, Saudi officials.

Fear of a MERS outbreak from migrant workers returning home has prompted other countries to take special precautions. In early June, the Philippine government began conducting thermal scans of incoming migrant workers from Saudi Arabia at the airport in Manila, and the Nepalese government wrote a letter to hospitals and laboratories, directing them to adopt precautionary measures when treating patients with respiratory illness.