The announcement of the 2nd domestic MERS case today is not surprising and doesn't represent a major change in the pattern of cases. This case, like the one before it, is in a traveling healthcare worker and its detection reinforces the importance of astute clinicians armed with the knowledge and tools to detect emerging viruses.
However, in light of this case, lingering questions should be revisited given the smoldering nature of this 2 year plus outbreak.
Do super spreaders exist?
The most dramatic feature of SARS was the existence of super spreaders. These Typhoid Mary like individuals were responsible for much of the global spread of SARS. With MERS however, evidence of super spreaders has not been definitively established although events suggestive of such spread exist. For example, in Abu Dhabi there is an case patient who may have been responsible for secondary spread to 27 additional cases. It is unclear, according to the WHO (at this time), whether these were all linked transmission events or from non-human sources. Additionally, the Al Hasa outbreak detailed in the NEJM is also suggestive.
I think that for all infectious diseases, super spreaders likely play a major role and MERS will turn out to be no different.
Is This a Public Health Emergency of International Concern?
The International Health Regulations provide WHO with a mechanism to declare a public health emergency of international concern (PHEIC) when events reach a certain threshold. The WHO is convening a meeting tomorrow to determine whether MERS meets that criteria. I think this is a difficult decision because, in a way, MERS has met this criteria over the last 2 years and nothing fundamentally different has occurred (granted the uptick in cases). Prior meetings have not resulted in such declarations. However, a PHEIC declaration may provide an impetus to countries with cases to provide more information about cases and the means by which they were infected.