I'm trying to find more information on a recent report that five more cases of MERS have been confirmed in Korea. The MERS Resources list now has a link to the Ministry of Health and Welfare's Korean-language news releases; Google Translate can give you the gist but no more.
Several countries have seen such imported cases since the MERS virus was first discovered in 2012, but the disease has never spread to more than a few other people, and the general consensus has been that MERS does not spread easily from human to human because it infects the lower respiratory tract, from which it can't easily reach other hosts.
But the Korean patient appears to have infected at least 22 family members, health care workers, and fellow patients at a hospital where he was treated from 15 May to 17 May. (The hospital's name has not been revealed.) No special precautions were taken during that time, because the patient had not yet been diagnosed.
The early phase of the disease, just after hospitalization and when symptoms are getting worse, is the time when patients tend to secrete the most virus, says Christian Drosten, a virologist at the University of Bonn in Germany.
“We know from Saudi Arabia that the virus can be transmitted during this time if people aren’t careful,” he says.
Yet in similar situations, hundreds of exposed contacts did not develop the disease, says Peter Ben Embarek, the point person on MERS at the World Health Organization (WHO). “Why does this happen in one situation and not the other?”
The simplest explanation for the "superspreading event," as scientists call this type of spread, is a lapse in infection control measures at the hospital, Ben Embarek says. The SARS virus, which is distantly related to MERS, is known to have spread widely in 2003 when tubes were placed in patients' airways for mechanical ventilation, a procedure that can cause the virus to become aerosolized. Whether Korea's first patient was intubated is unclear. “We don’t really know what happened during those 3 days,” Ben Embarek says.
Other explanations are being looked at as well. The patient could be carrying a slightly different strain of the virus, or Koreans may be more susceptible to the disease than other populations, Ben Embarek says.
One important piece of evidence will be the genetic sequence of the virus. Ben Embarek says Korea has agreed to share samples with several labs working on MERS, including at Hong Kong University (HKU) in China and Erasmus MC in Rotterdam, the Netherlands.
“We hope to have sequence analysis very soon so we can see any recent changes,” Ben Embarek says. “I don’t know if the samples have left the country or not, but I know there is an agreement that it will happen.” (Marion Koopmans of Erasmus MC tells ScienceInsider she has not heard from Seoul yet; so does HKU's Malik Peiris. "We have indicated our willingness to help. Have not heard anything concrete yet," Peiris e-mailed today.)