Clinical Infectious Diseases

(Prepared by the section editor)—The coronavirus of Middle Eastern respiratory syndrome (MERS) has caused respiratory illnesses in the Middle East since it was first identified in mid-2012. As of 28 August 2017, there have been 2067 cases of MERS reported to the World Health Organization, including at least 720 deaths (case fatality rate of 34.8%). Cases have been reported from 27 countries, all with the index case originating in the Middle East, with 82% of cases having been reported by Saudi Arabia. The number of deaths to date (720) is close to the 724 deaths that occurred in the severe acute respiratory syndrome outbreak of 2002–2003. In the 1-year period from 1 July 2016 to 30 June 2017, 251 cases of MERS were reported, of which 243 (97%) were reported from Saudi Arabia, 3 from Qatar, 2 from the United Arab Emirates, and 1 each from Oman, Austria (with travel from Saudi Arabia), and Thailand (with travel from Kuwait). Thirty-seven (15%) of the 243 Saudi Arabia cases were asymptomatic contacts of known MERS cases. Of the 243 cases reported by Saudi Arabia in this period, 67 (28%) involved nosocomial transmission, mainly in healthcare workers (60%); 14 (6%) involved household contact; 74 (30%) were related to camel or camel product contact; and the largest group of 84 (35%) had no apparent risk factors. The MERS virus has been found in camels throughout Africa including Egypt where more than 90% of camels have serological evidence of past infection. However, serological studies have not demonstrated evidence of antibodies in any of the humans who had close contact with these camels. It is a mystery as to why Saudi Arabia is the epicenter of MERS compared to other Middle Eastern countries or why it has not occurred (to my knowledge) in African countries. The main hypothesis that has been given is that unrecognized cases occur in these countries or that the coronavirus is less virulent in these countries. However, the Egyptians have detected cases of avian influenza, and it is a stretch to think that they are unable to suspect and detect the coronavirus of MERS. Furthermore, at least 1 isolate from an Egyptian camel was genetically very similar to a MERS coronavirus that is infecting humans. There is also no solid information as to the source of MERS in 35% of cases that occurred in Saudi Arabia in the year as described above. Inadequate histories probably play a role. In addition, 1 small study demonstrated that any contact with other individuals who had direct contact with camels might play a role in transmission.