Middle East respiratory syndrome (MERS): A new zoonotic viral pneumonia

Cunha, Cheston B; Opal, Steven M

Coronaviruses are enveloped single stranded RNA viruses. The glycoprotein spikes (S) surrounding the spherical virion gives the virus its characteristic "halo appearance", i.e., a corona on electron microscopy. Six coronavirus subgroups are known human pathogens, the α coronavirus subgroup includes 229E and NL229E, and the β coronavirus subgroup includes OC43, HKU1, SARS-CoV, and MERS-CoV. Coronaviruses have relatively large genome (26-32 kb) and all six human coronavirus subgroups have been cultured in vitro except for the β coronavirus subtype HKU1. 1,2 MERS-CoV is the first C lineage β coronavirus known to infect humans. Although MERS-CoV is genetically closely related to other β coronaviruses isolated from bats in Europe, Mexico, Africa, and Hong Kong, dromedary camels are the likely reservoir for MERS-CoV in the Arabian Peninsula. 5 Although both SARS and MeRS are caused by coronaviruses, SARS was characterized by efficient human transmission and relatively low mortality rate. In contrast, MeRS is relatively inefficiently transmitted to humans but has a high mortality rate. Given the potential overlap in presentation and manifestation, it is important to understand the clinical and epidemiologic differences between MeRS, SARS and influenza.