Middle East Respiratory Syndrome

Abstract

Between September 2012 and January 20, 2017, the World Health\nOrganization (WHO) received reports from 27 countries of 1879\nlaboratory-confirmed cases in humans of the Middle East respiratory syndrome\n(MERS) caused by infection with the MERS coronavirus (MERS-CoV) and at least 659\nrelated deaths. Cases of MERS-CoV infection continue to occur, including\nsporadic zoonotic infections in humans across the Arabian Peninsula, occasional\nimportations and associated clusters in other regions, and outbreaks of\nnonsustained human-to-human transmission in health care settings. Dromedary\ncamels are considered to be the most likely source of animal-to-human\ntransmission. MERS-CoV enters host cells after binding the dipeptidyl peptidase\n4 (DPP-4) receptor and the carcinoembryonic antigen–related cell-adhesion\nmolecule 5 (CEACAM5) cofactor ligand, and it replicates efficiently in the human\nrespiratory epithelium. Illness begins after an incubation period of 2 to 14\ndays and frequently results in hypoxemic respiratory failure and the need for\nmultiorgan support. However, asymptomatic and mild cases also occur. Real-time\nreverse-transcription–polymerase-chain-reaction (RT-PCR) testing of\nrespiratory secretions is the mainstay for diagnosis, and samples from the lower\nrespiratory tract have the greatest yield among seriously ill patients. There is\nno antiviral therapy of proven efficacy, and thus treatment remains largely\nsupportive; potential vaccines are at an early developmental stage. There are\nmultiple gaps in knowledge regarding the evolution and transmission of the\nvirus, disease pathogenesis, treatment, and prospects for a vaccine. The ongoing\noccurrence of MERS in humans and the associated high mortality call for a\ncontinued collaborative approach toward gaining a better understanding of the\ninfection both in humans and in animals.