Middle East Respiratory Syndrome

Between September 2012 and 7 October 2016, 1806 laboratory-confirmed human cases of Middle East Respiratory Syndrome (MERS) caused by infection with the MERS coronavirus (MERS-CoV) from 27 countries, including 643 deaths (crude case fatality proportion 36%), have been reported to the World Health Organization (WHO). MERS-CoV continues to cause sporadic human infections within the Arabian Peninsula, periodic non-sustained human-to-human transmission with prominent healthcare-associated outbreaks, and occasional imported cases into other countries. Dromedary camels are considered the most likely source of animal-to-human infection. MERS-CoV enters host cells after binding the dipeptidyl peptidase-4 receptor and the carcinoembryonic antigen-related cell adhesion molecule 5 cofactor ligand and replicates efficiently in human respiratory epithelium. Illness begins after a 2-14 day incubation period, frequently leading to hypoxemic respiratory failure and requirement for multi-organ support. However, as identified from surveillance and contact tracing, asymptomatic and mild cases also occur. Real-time reverse-transcription polymerase chain reaction (rRT-PCR) testing of respiratory secretions is the mainstay for diagnosis and lower respiratory tract samples among seriously ill patients have the greatest yield. There is no antiviral therapy of proven efficacy, treatment remains largely supportive and potential vaccines are at an early developmental stage. Multiple gaps in knowledge exist regarding virus evolution, transmission, disease pathogenesis, treatment, and prospects for a vaccine. The ongoing occurrence of MERS in humans coupled with its high mortality calls for a continued collaborative “One Health” approach towards better understanding of both human and animal infections.