With 18 confirmed cases, and reportedly more than 680 persons either in isolation or quarantine, the next week to ten days will be critical in South Korea's MERS outbreak as it will determine whether or not the virus has managed to enter the community.
From a standing start less than two weeks ago, when we first learned of an imported case with recent travel history to the Middle East, South Korea has gone from having no cases to being the 4th hardest hit nation on Earth; exceeded only by Saudi Arabia, the UAE, and Jordan.
While all of the cases so far have been linked to the index case, or the health facilities where he was seen, we know of instances where the greater community may have potentially been exposed, most famously by the 44 year-old Korean male who traveled (against doctor's orders) to Hong Kong and Mainland China and is now hospitalized in Guangdong Province.
With an incubation period of between 2 and 14 days, we won't know for another week or more if Korea (and Hong Kong & Mainland China) have dodged a bullet here.
There have been multiple reports of `suspected cases' in the community, such as in this Korea Times report Suspected MERS case detected in elementary school , but thus far none have been announced as being positive.
Another report, also from the Korea Times, is Breaking: Suspected MERS patient dies. Here a patient who apparently had contact with the index case was admitted to the hospital and died on Monday.
MERS has not been confirmed in either of these cases, but if either test comes back positive, it would represent serious challenges to the Korean containment efforts.
While many `suspected cases' are likely to end up false alarms, authorities can't afford to ignore any of them. The magnitude of their problem today has come, at least in part, to underestimating the transmissibility of the virus.
For reasons that are less than clear, Korea's MERS outbreak has spread faster than any outbreak we've seen outside of Saudi Arabia or the UAE. Speculation has included the idea that the index case is a `superspreader', while a Reuters report this morning - S.Korea fights to contain MERS outbreak, considers tough measures - discusses another possibility.
In South Korea, one elderly patient who had a history of kidney ailment was in a serious condition, with weak vital signs requiring him to be on cardiac and respiratory support, the head of the Korean Society of Infectious Diseases, Kim Woo-joo, told a briefing.
"I've been asking myself whether there may be a genetic factor, if anything makes (Koreans) more vulnerable, but so far there's no evidence," said Kim, who is advising the Health Ministry on the outbreak.
Although unproven, there is a little precedent to this idea, as we've seen studies showing some populations more susceptible to certain types of viral infections (see A Genetic Predisposition To Severe Flu Infection) than others.
The other notion, that of a `superspreader', also has some history.
During the SARS outbreak of 2003 (believed to be far more contagious than MERS), studies found most infected persons would only infect 1 or perhaps 2 additional people, and sometimes none. But a small percentage of those infected were far more efficient in spreading the disease, with some responsible for 10 or more secondary infections.
SARS jumped from Asia to North America courtesy of a single superspreader -- a Chinese doctor who had treated cases in Guangdong and who stayed at the Metropole Hotel in Hong Kong to attend a wedding. He passed the virus on to roughly a dozen people during his stay, including one who took the virus on to Toronto, Canada.
Other super spreaders in Singapore, and Toronto, helped give `legs’ to the epidemic. Without their help, SARS might never have spread beyond Asia.
This super spreader phenomenon gave rise to the 20/80 rule, that 20% of the cases were responsible for 80% of the transmission of the virus (see 2011 IJID study Super-spreaders in infectious diseases).
There are other possibilities, of course - including a major breakdown in infection control procedures at these healthcare facilities, more favorable climatic conditions for spreading the virus, and the slim possibility that the virus has somehow changed.
For now, we've far more questions than answers.
Stay tuned. It could be a bumpy week.