As the outbreak of MERS cases in South Korea continues it appears that what is responsible for the 30--2 of which have been fatal and one of which was imported to China--is a combination of lax infection control coupled with a possible super-spreader event. This camel and bat-linked coronavirus, which has killed about 36% of the 1200 people it has infected thus far, has now been reported in 16 nations (including the US for those of you who have forgotten).
To recap the events: mid-May a man who traveled to the MERS epicenter, the Middle East, returned to South Korea and was subsequently diagnosed with MERS. Being the 1st MERS case in South Korea and with a consequent delay in diagnosis patient's who were co-located were exposed and infected (primary transmission) then went on to infect others (secondary tranmission) who then went on to infect others (tertiary transmission, which has been confirmed in 2 cases).
This cluster, which is exclusively hospital-based thus far, has vaulted South Korea to the #3 MERS country, behind Saudi Arabia and the UAE. Such a cluster reinforces the need for meticulous infectious control when dealing with a respiratory virus like MERS that has proven adept at exploiting lapses in infection control. South Korean authorities have since apologized for their handling of the initial stages of this outbreak which have led to over 1300 people being monitored after contact with case patients.
Also, the index patient is responsible for infected at least 11 (maybe 22) other individuals (Ro = 11 - 22) clearly putting this man in the category of a super-spreader as his disproportionate contagiousness has clearly fueled this outbreak (similar to what occurred with the related SARS in 2003).
It is important to remember, at this stage, that no community transmission has occurred in South Korea and, though it is a possibility, swift action on the part of public health authorities can extinguish the outbreak. What also must be emphasized to clinicians world-wide is that MERS (and other infectious diseases) can appear anywhere and, to paraphrase Louis Pasteur, prepared minds are the ones that are lucky enough to discover them before too much damage is done.