MERS-CoV cases exposed in the Arabian Peninsula were identified in the European Union and in Tunisia mainly while seeking medical care. This has resulted in secondary transmission. The majority of travels from the Arabian Peninsula however, are destined to Asian countries which suggests that the risk of introductions exists also in Asia . No cases have been reported there to date, despite enhanced surveillance in some countries. It is noteworthy that no infected cases have been detected outside the Arabian Peninsula since May 2013. The striking overrepresentation of men among cases in the first months balanced over time. This can be partly explained by the higher proportion of female HCW among recently reported nosocomial transmissions. In a similar fashion, the median age of cases has decreased.
Our assessment of the severity of the disease and outcomes is based on available data at the time of the reporting from the country and may result in under ascertainment of severe outcomes. At the same time, the proportion of cases admitted to intensive care and the CFR has decreased over time, which may be a reflection of enhanced surveillance activities.
‘Superspreading’ events or cases were interpreted as a key cause for the progression of the severe acute respiratory syndrome (SARS) outbreak in 2003 . The large nosocomial cluster of MERS in Al Hasa, Saudi Arabia, involving up to 23 cases has some similarities with such events. It could have been caused by multiple zoonotic or human introductions in the community or inconsistencies in applying appropriate infection prevention measures in health facilities. It raises concerns about the ‘superspreaders’ as a source of extended transmission chains. The pandemic potential of MERS-CoV remains low. The basic reproduction number (R0) is estimated at 0.69, lower than the R0 for pre-pandemic SARS (0.80) and well below the epidemic threshold of 1 .
The significant proportion of caregivers likely infected in hospitals or at home played a role in transmission of MERS-CoV and is of concern. No secondary transmission has been associated with long-haul medical evacuation, suggesting that appropriate infection measures were applied and effective.
The fact that all but one of the primary cases in the known clusters are adult men originating from the Arabian Peninsula, suggests behavioural risk factors may play a role exposing them directly or indirectly to the reservoir of MERS-CoV. The severity of the diseases and fatal outcomes of the majority of the primary cases hinders effective exploration to identify risk factors.