Infection with Middle East respiratory syndrome coronavirus.

T he Middle East respiratory syndrome coronavirus (MERS-CoV) was first recognized as a new febrile respiratory illness in Saudi Arabia in June 2012. As of September 21, 2015, the WHO reported 1569 laboratory-confirmed cases, including at least 554 related deaths. Cases have been reported in 26 countries ; however, the majority of cases have occurred in Saudi Arabia (79%) and South Korea (13%) (1). MERS-CoV infection has been documented in dromedary camels; evidence suggests that they are the most common source of animal-to-human transmission (2). Although the exact mode of transmission from camels is unknown, the presence of high viral loads in the upper respiratory system of infected camels suggests that transmission occurs through close contact (2). Human-to-human transmission of MERS-CoV has been demonstrated among close household contacts (3). However, sustained community transmission has not been observed. In a cross-sectional serosurveillance study involving 10,009 individuals in Saudi Arabia, positive serology was documented in only 0.15% of individuals sampled (4). Transmission within health care settings has been a predominant feature of MERS-CoV infection, and has been attributed to breaches of infection prevention and control practices (5). Coronaviruses are a family of single-stranded RNA viruses. MERS-CoV is the sixth coronavirus and the first lineage C beta-coronavirus known to infect humans. Severe acute respiratory syndrome coronavirus is of lineage B (6). MERS-CoV enters cells via a common receptor, the dipeptidyl peptidase-4, and it infects type I and type II alveolar cells (7). The virus has primarily been detectable in respiratory secretions, with the highest viral loads in the lower respiratory tract (8). The median incubation period of MERS-CoV infection is 5.2 days, but it can be as long as 14 days (9). The most severe cases of MERS-CoV infection have been reported in adult patients with underlying comorbidities, including diabetes mellitus, ischemic heart disease, end-stage kidney disease or immunosuppression (9,10). However, severe infection may also occur among younger patients, especially health care workers. The disease spectrum ranges from asymptom-atic infection to rapidly progressive multiorgan failure. The most common clinical features in severe cases are fever (71%), cough (68%), dyspnea (66%) and gastrointestinal symptoms (32%) (9). Laboratory abnormalities commonly associated with severe MERS-CoV infection include leukopenia, lymphocytopenia and thrombocytopenia, in addition to elevated serum levels of cre-atinine, lactate dehydrogenase and liver enzymes (9). Initial chest radiographs are abnormal in the majority of symptomatic patients. Findings range from minimal abnormality to extensive bilateral infiltrate consistent …