The latest export from the Middle East isn’t oil or textiles or natural gas: it’s a novel coronavirus that causes a disease dubbed Middle East respiratory syndrome, or MERS. MERS has been in the news recently, as there is an ongoing outbreak of the disease in South Korea, which has thus far infected 150 people and caused 16 deaths. But what is it exactly, and how likely is MERS to cause a global pandemic?
Identified in 2012, MERS is caused by a coronavirus that results in viral pneumonia, which can be deadly in older patients with underlying health complications. In terms of symptoms, it is very similar to another coronavirus disease: SARS, or severe acute respiratory syndrome, which caused a major epidemic originating in China in 2002 and 2003. Patients typically develop fevers, coughing, sneezing, viral malaise, with smaller subsets presenting with diarrhea and/or nausea. In rare cases, the disease progresses to cause kidney failure, respiratory distress, and potentially multi-organ failure.
Structure of a coronavirus, 70-120 nanometers in diameter. Graham et al., Nature Reviews Microbiology 2013.
The current outbreak of MERS in Korea was caused by a single patient, a 68-year-old man returning from a business trip. He was treated at four different hospitals, and it is thought that a combination of higher-than-average viral load and poor room ventilation resulted in dissemination despite the difficulty with which MERS is normally transmitted. Meanwhile, the economic impact on Korea has been tremendous, as hundreds of schools and public buildings have been closed to protect against the spread of infection.
Though it is believed that the outbreak in Korea will be controlled in the near future with minimal continued spreading, a much more daunting challenge is how to prevent transmission in the Middle East. MERS is actually a zoonotic infection, meaning that it jumps from animals to humans. Like many coronaviruses, it is thought to originate in bats. A much more considerable problem, however, is that the virus has adapted to another animal host: camels. Indeed, the MERS virus is endemic in camel populations, but the mode of transmission to humans remains frustratingly unaddressed. Despite the fact that more than 80% of infectious cases occur in Saudi Arabia, little effort appears to have been made to uncover the particular contact these individuals had with animals.
Unfortunately, MERS represents yet another example where resources have largely been misallocated. The mere collection of data cataloguing the interactions between MERS patients and camels, such as whether contact with urine, or saliva, or milk resulted in the greatest incidence of disease, could have helped prevent the outbreak in Korea entirely. There are additional unanswered questions regarding the transmission from camels to humans: it is currently unknown why the disease is totally absent in Africa despite the large camel populations that carry the virus and close interactions between these animals and humans.
Ultimately, this outbreak demonstrates the importance of actually addressing the root cause of viral pathogenesis. All things considered, the people of Korea are somewhat fortunate that the virus wasn’t a more lethal species or variant. As the world gets smaller and intercontinental travel continues to expand in prevalence and scope, these seemingly random outbreaks will likely become more and more common unless the underlying mechanisms of infection are better understood. Additionally, as with all viral infections, there is the massive risk that the virus will mutate to a more effective form. This is a particular concern for zoonotic viruses, because human immune systems are unlikely to have had the opportunity to develop memory responses against these species. Notable zoonotic outbreaks include the 2009 H1N1 swine flu epidemic and, as previously mentioned, the SARS epidemic of 2002/2003.
Incidence of confirmed cases of MERS-CoV in the Middle East over time. Credit: Dr. Ian M Mackay
Hopefully these unfortunate events catalyze a push for additional research in the Middle East. While the virus has yet to accumulate significant mutations and all current cases demonstrate a direct route of transmission, more new infections go unchecked. As they do, it becomes more and more likely that a virulent strain will develop. the human and economic costs of which could be astronomical. Current estimates suggest that as much as $900 million has been lost by South Korea’s normally robust tourism industry alone. Unless there is a vigorous effort made on the other side of the world, however, these figures may pale in comparison to subsequent pandemics.
