A visitor to South Korea would be hard-pressed to find a camel anywhere other than in a zoo, but the country’s ongoing outbreak of Middle East Respiratory Syndrome, or MERS, can likely be traced to camels thousands of miles away. The virus has infected 122 people and killed 10 in South Korea over the past three weeks and camels are the most likely source for the original human infection.
In Saudi Arabia, where the virus was first identified in a human, in 2012, camels play a critical role in the national economy and the livelihood of pastoralists – but they also carry MERS. While the outbreak in South Korea has prompted public health officials to call for faster diagnosis and improved hospital protocols, some scientists are working to develop ways to prevent outbreaks at their source – the one-humped ungulate known as the dromedary camel.
Lab tests of preserved biological samples show that MERS has infected camels in Saudi Arabia since at least 1992, which means camels exchanged the virus amongst one another for decades before the first human contracted it. W. Ian Lipkin, director for the Center for Infection and Immunity at Columbia University, swabbed camels throughout Saudi Arabia in 2013 and found that 74 percent had been exposed to the virus at some point in their lifetime – probably when they were young. Since 2012, the vast majority of MERS cases worldwide – 85 percent – have occurred in Saudi Arabia. About 40 percent of people who contract MERS will die from it, but camels don’t seem to be all that bothered –they suffer from a runny nose for a few days but recover within a week.
“There’s a lot of evidence now that this is the route by which many people become infected,” he says. But soon after Lipkin first published his survey in 2014, some farmers in Saudi Arabia protested its implications by posting photos to Twitter showing them kissing their camels during a MERS outbreak.
الله يستر من فيروس كورونا ولكن ما نقدر نصبر عن الابل لها محبة خاصة والصورة تغني عن الكلام . pic.twitter.com/urHIUzlr5J
â€” الصحفي نواف الحدباء (@nawaf4908) May 9, 2014
It’s not entirely clear how MERS might have transferred from camels to humans, but Richard Bowen, a biomedical researcher at Colorado State University, believes the virus spreads through close contact with the respiratory system of an infected camel – perhaps by being in the line of fire when it sneezes.
Bowen has swabbed the noses of camels at his research facility in Fort Collins, Colo. with a Q-tip and found that a single camel can exude 10 million units of the virus on a single swab – that’s enough to infect 10 million cell cultures. He doesn’t know how many units are necessary to infect a camel or human. Still, he says, “There’s a ton of virus coming out of the noses of those camels.”
Right now, the strain of MERS that is typically found in victims is not considered particularly contagious – an infected person must come into close contact with an uninfected person in order for it to spread. But last year, Esam Ashar, a medical virologist at King Abdulaziz University in Jeddah, found an airborne version of the virus in a barn full of camels.
When severe acute respiratory syndrome, a related virus known as SARS, broke out in 2002, Chinese officials in Guangdong Province ordered the killing of 10,000 civet cats because the species harbored the virus. Wayne Marasco, an infectious disease expert at Harvard Medical School, says that approach will never work for MERS, because camels are highly respected animals and play such a critical role in the economic livelihood of their owners. Camels are a regular mode of transportation for people throughout the region and are sought out for their milk, meat and urine. Farmers and owners often view them as companions.
Gabbay agrees that the high value of camels in Saudi Arabia would make it difficult to remove them altogether. The symbolism these beloved animals hold in daily life also often trumps warning that they could make their owners ill. Despite these challenges, scientists continue to look for ways to work with camels to ensure that MERS does not spread further. Bowen says it would also be difficult to cure any of these camels once they are infected. First of all, the virus is hard for owners to diagnose since a camel's symptoms are relatively mild. Furthermore, few anti-viral drugs exist and any such drug would likely be too expensive to use widely.
Instead, Bowen is working with the U.S. National Institutes of Health to test a vaccine that would protect camels from MERS. A vaccine could likely be made for far cheaper than anti-viral drugs. Even so, he says one remaining challenge will be the cost of immunizing the 800,000 camels in Saudi Arabia against a virus that really only causes them to have a runny nose.
“Normally, people don't want to spend money on vaccines if it’s not really harming the animal,” Bowen says. “So you have to convince all the camel owners, or the government would have to require that the camels be immunized.”
Camels in Saudi Arabia are owned by people across a broad array of social classes -- Gabbay says they can be bought for anywhere between $1,000 to a million dollars -- and receive varying levels of care which might make it difficult for the government to roll out a comprehensive immunization program.
“There are camels that are cared for better than children in the U.S. It’s like raising thoroughbred horses,” Bowen says. “But then there are these large groups of camels that don’t have any kind of care.”
And while Saudi Arabia might be able to underwrite the expense for nationwide immunizations, as one of the world’s top exporters of oil and one of the wealthiest countries in the region, MERS has also been found in camels in Jordan and Oman. In 2010, there were about 16 million camels throughout the Middle East – one for every 21 people.
There is a precedent for this approach, though – the U.S. Department of Agriculture says American farmers have saved hundreds of millions of dollars by immunizing cattle for a bacteria called brucellosis rather than letting it infect both livestock and their products. In 1953, the bacteria could be found in at least 124,000 herds in the U.S. and consumers were at risk of contracting it by consuming contaminated milk or meat from these animals. Today, there are only 100 or 200 cases of brucellosis a year thanks to widespread vaccination.
But Lipkin says a camel vaccine for MERS is still a long way off, and may not even be the best solution. He thinks it makes more sense in the long-term to develop drugs for the handful of patients who contract the virus, rather than pay to immunize millions of camels against it. Last week, he visited Saudi Arabia to meet with the Ministry of Agriculture and the Ministry of Health which have requested that he begin working with researchers there to monitor the disease in camels and conduct research to develop rapid diagnostics and potential treatments for people.