Summary
Between September 2012 and January 20, 2017, the World Health
Organization (WHO) received reports from 27 countries of 1879
laboratory-confirmed cases in humans of the Middle East respiratory syndrome
(MERS) caused by infection with the MERS coronavirus (MERS-CoV) and at least 659
related deaths. Cases of MERS-CoV infection continue to occur, including
sporadic zoonotic infections in humans across the Arabian Peninsula, occasional
importations and associated clusters in other regions, and outbreaks of
nonsustained human-to-human transmission in health care settings. Dromedary
camels are considered to be the most likely source of animal-to-human
transmission. MERS-CoV enters host cells after binding the dipeptidyl peptidase
4 (DPP-4) receptor and the carcinoembryonic antigen–related cell-adhesion
molecule 5 (CEACAM5) cofactor ligand, and it replicates efficiently in the human
respiratory epithelium. Illness begins after an incubation period of 2 to 14
days and frequently results in hypoxemic respiratory failure and the need for
multiorgan support. However, asymptomatic and mild cases also occur. Real-time
reverse-transcription–polymerase-chain-reaction (RT-PCR) testing of
respiratory secretions is the mainstay for diagnosis, and samples from the lower
respiratory tract have the greatest yield among seriously ill patients. There is
no antiviral therapy of proven efficacy, and thus treatment remains largely
supportive; potential vaccines are at an early developmental stage. There are
multiple gaps in knowledge regarding the evolution and transmission of the
virus, disease pathogenesis, treatment, and prospects for a vaccine. The ongoing
occurrence of MERS in humans and the associated high mortality call for a
continued collaborative approach toward gaining a better understanding of the
infection both in humans and in animals.
MERS-CoV was first identified in September 20121 in a patient from Saudi Arabia who had hypoxemic
respiratory failure and multiorgan illness. Subsequent cases have included
infections in humans across the Arabian Peninsula, occasional importations and
associated clusters in other regions, and outbreaks of nonsustained
human-to-human transmission in health care settings (Fig. 1).
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