"Superspreader" hospitals amplify MERS outbreak in Korea

In a previous post, I described how a single "superspreader" person could have caused the large outbreak of MERS in Korea. MERS is usually not considered highly contagious, possessing a reproduction number of only 1, i.e. the typical infected person will spread MERS to one other person. However a person containing a lot of virus in his body that also happens to contact a large number of people could spread MERS to many people. Indeed, some have hypothesized that the index case, the person who brought MERS from Saudi Arabia to Korea, was such a superspreader.

Now it appears the problem was not a single superspreader, but multiple superspreaders that arose through a key vulnerability in the system, the hospitals. It is less important how infectious an individual is, and more important how many contacts she has. Ironically several large hospitals have served as a nexus for spreading the virus by facilitating the contact between unidentified infected individuals and a large crowd of bystanders, many of whom possess weakened immune systems. A Reuters article chronicles one such example in which "Patient 14" (the 14th person identified in Korea with MERS) may have spent 2.5 days in a premiere Seoul hospital exposing nearly 1000 people to the virus, among whom as many as 55 may have been infected (Reuters):

"The man who became South Korea's MERS patient number 14 waited two-and-a-half days in the emergency ward for a bed to open at a prestigious Seoul hospital – not an unusually long time for the city's top medical centers.

By the time the 35-year-old was suspected of infection with Middle East Respiratory Syndrome (MERS), nearly 900 hospital staff, visitors and patients had been through the emergency ward. Of those, 55 were infected with MERS, including four elderly patients who have died while the rest are in quarantine, putting the hospital at the center of an outbreak that has infected 122, with 10 dead."

One issue is that the popular hospitals in Korea are overcrowded with people waiting for days in the Emergency Room for a bed. The result is a large crowd of patients and their families in a small confined area before the patients can be diagnosed and treated.

It is in these close quarters that hospitals amplified the MERS outbreak by allowing the virus to jump from one superspreader to another with each superspreaders possessing a high contact number. Indeed in the prestigious Samsung Hospital, one of superspreaders turned out to be a hospital worker who became infected:

"Among the cases at the Samsung Medical Center was an emergency ward orderly who worked for days after developing symptoms, coming into contact with more than 200 people, the hospital said."

Fortunately, medical investigators have figured out the problem, and in this particular case, they closed down the hospital:

"The Samsung Medical Center, a prominent hospital in the capital, said it was suspending all non-emergency surgery and would take no new patients to focus on stopping MERS after more than 70 cases were traced to it."

From a public health standpoint, identifying and closely monitoring these superspreader locations is the key to containing the outbreak. It is important to mention that these superspreader scenarios are much less dangerous than the highly unlikely possibility that the MERS virus has mutated to a more contagious form.

Indeed, there seems to have been some abatement in the outbreak. I plotted the number of new MERS cases in Korea over the past two weeks (Figure 1). The curve is trending downwards which is a good sign. Hopefully, the downward slope will continue aided by the identification and containment of the "superspreader" hospitals that have amplified this outbreak.

Figure 1. Number of new cases of MERS in Korea each day from June 6 to June 18 (data from Reuters).