MERS-coronavirus: From discovery to intervention

Widagdo, W.; Okba, Nisreen M.A.; Stalin Raj, V.; Haagmans, Bart L.

MERS patients require proper quarantine measures to hinder the spread of the MERS-CoV to other susceptible individuals. Although several studies performed in Saudi Arabia and South Korea indicated that human-to-human transmission is relatively limited, it has been found to be crucially important, especially in the hospital outbreaks [5, 36, 37] . Inefficient human-to-human transmission is partly due to the tropism of MERS-CoV. Autopsy results from one fatal human MERS case and ex-vivo experiments using human lung explants showed that this virus infects the lower respiratory tract epithelium [38, 39] . These observations are consistent with the fact that in most cases MERS-CoV isolation from human samples was successful only when lower respiratory tract samples were used [3, 40] . Although it is possible to detect MERS-CoV in the upper respiratory tract, viral RNA levels are generally very low compared to the lower respiratory tract [40] [41] [42] . This restricted tropism of MERS-CoV in the lower respiratory tract is supported by the distribution of its host receptor. DPP4 is expressed in the lower but not in the upper human respiratory tract epithelium [43] .