What MERS Shows Us About Emerging Diseases
June 12, 2015
By: Seth Gannon
For weeks South Korean health officials have been working to contain the spread of Middle East Respiratory Syndrome (MERS), an acute respiratory illness characterized by fever, cough, shortness of breath, and, in past outbreaks, a 30-40% fatality rate. The underlying virus, MERS coronavirus (MERS-CoV), is relatively difficult to transmit, requiring close contact, although the precise mechanism is not well understood. But since an infected patient returned from travel in Saudi Arabia and the United Arab Emirates (UAE) in May, South Korea has confirmed more than 100 infections, recorded nine deaths, quarantined approximately 3,000 people, and closed over 2,000 schools and universities. What does this outbreak tell us? In some particulars MERS is unusual, but it represents a general archetype for emerging infectious diseases: zoonotic in origin, carried across continents by an infected air traveler, initially undiagnosed, bringing fear and economic disruption, and spreading most quickly through vulnerable populations.
Before 2002, human coronaviruses (four were known) were responsible for mild infections of the upper respiratory tract and posed no serious global threat. That changed with the appearance of Severe Acute Respiratory Syndrome, or SARS. The 2002-03 SARS outbreak originated in Guangdong, China, spread to four continents, infected more than 8,000 people, killed 774, and galvanized a global containment effort. (The world has reported no cases of SARS since 2004.) Scientific investigation of the novel coronavirus responsible, SARS-CoV, revealed that it was zoonotic — it came to humans from non-human animals, mostly likely animals for sale in a Guangdong marketplace.
Since it appeared in humans in Jordan and Saudi Arabia in 2012, investigations of MERS-CoV have similarly pointed to a zoonotic origin. This sixth known human coronavirus shares substantial genetic material with coronaviruses found in bats. “Since human-bat contact is limited,” write Ahmad Sharif-Yakan and Souha Kanj of the American University of Beirut Medical Center, “camels have been implicated as probable intermediate hosts. MERS-CoV appears to have been circulating in dromedary camels for over 20 years.” They continue: “MERS-CoV has been detected [from] nasal swabs of three camels in Qatar and was linked to two confirmed human cases with high similarity upon sequencing, suggesting a possible respiratory mode of transmission.” A case study in The New England Journal of Medicine looked at a 43-year-old Saudi man, owner of a herd of nine camels, who died of MERS in November 2013. The study concludes: “Serologic data … suggest that this fatal case of human MERS-CoV infection was transmitted through close contact with an infected camel.”
This is no huge surprise. A 2008 study published in Nature analyzed 335 infectious diseases that emerged between 1940 and 2004, and drew two overarching conclusions. First, emerging infectious diseases “have risen significantly over time after controlling for reporting bias.” Second, of the 335 diseases studied, 60.3% were zoonotic in origin, and these zoonoses “are increasing significantly over time.” Explaining the rise in zoonotic disease, the World Health Organization cites “environmental changes, human and animal demography, pathogen changes and changes in farming practice.” The World Organization for Animal Health offers a similar list (globalization, industrialization, changing agricultural systems) and concludes that “the scope, scale, and world-wide impact of zoonoses we are facing today have no historical precedent.”
It is clear from the numbers that MERS, even now, is not the next SARS. As Daniel Lucey of the Georgetown University Medical Center writes in a report for the CSIS Korea Chair, in most patients without lung disease, kidney disease, immunodeficiency, or diabetes, “the MERS virus causes less severe or mild illness, or even no symptoms at all.” In the first couple years after the virus was identified, only a handful of MERS cases traveled beyond the Middle East.
Of course, that streak ended when South Korea’s first infected patient — the 68-year-old index case for the current outbreak — returned home from travel to Saudi Arabia and UAE and visited a number of hospitals with a cough and fever. (Had doctors known of his travel, they might have diagnosed and contained the disease, as with imported MERS cases in the United States and elsewhere.) It has become a cliché to say that in a globalized world, emerging infectious diseases “are only a plane ride away.” But Korea’s outbreak — even if MERS is less contagious than SARS and will soon be contained — demonstrates again that the cliché carries a lot of truth.
Like many outbreaks, MERS in South Korea has moved most quickly through vulnerable populations, particularly patients in those hospitals visited by the index case. “Hospitals can become amplification points,” CDC Director Thomas Frieden tells Time. “It’s the case in measles, it’s the case for drug-resistant tuberculosis, it’s the case for MERS and SARS and Ebola. That’s where sick people go and that’s where vulnerable people are. It really emphasizes the importance of good infection control in the health care system.” This is particularly true in South Korea, where family members stay with patients in the hospital and do much of the nursing work. (An interesting New York Times feature collected readers’ anecdotes of South Korean hospitals.) A CDC advisory written before the current outbreak captures this phenomenon: “MERS-CoV has spread … through close contact, such as caring for or living with an infected person.”
New and unusual contagions are scary, and in particular bring fear of contact and public spaces. As reported in the Wall Street Journal, consumers and tourists are staying home, and South Korea is seeing economic repercussions. President Park Geun-hye called for “citizens to refrain from excessively reacting to MERS for the sake of the economy.” As seen with Ebola last fall, rumors amplify the fear, and South Korean police have actually arrested eight people for “business obstruction and libel” related to MERS — in other words, for claiming that the disease is in hospitals it isn’t.
MERS is not SARS or Ebola, and as Daniel Lucey argues, it will soon be contained in South Korea. But its emergence has had real consequences on the Arabian peninsula and now on the Korean. It has exposed weaknesses in South Korea’s hospital system and gaps in disease detection, isolation, and control. And it has demonstrated the concerns motivating the Global Health Security Agenda (GHSA), an international partnership to prevent and respond to infectious disease outbreaks. No country is immune to the arrival of novel diseases – often zoonotic in origin, slow to be diagnosed, hitting vulnerable populations hardest, and disrupting health, trade, travel, and education. The G-7, meeting in Germany on June 7-8 with MERS in the news, reaffirmed its support for the GHSA and committed to achieve the Agenda’s goals in at least 60 countries. South Korea is the next GHSA chair, and when it hosts the annual summit in September, the recent experience with MERS will be close at hand.