Asymptomatic Middle East Respiratory Syndrome Coronavirus (MERS-CoV) infection: Extent and implications for infection control: A systematic review

Background: The Middle East Respiratory Syndrome Coronavirus (MERS-CoV) emerged in 2012 and attracted an international attention as the virus caused multiple healthcare associated outbreaks. There are reports of the role of asymptomatic individuals in the transmission of MERS-CoV, however, the exact role is not known. Method: The MEDLINE/PubMed and Scopus databases were searched for relevant papers published till August 2018 describing asymptomatic MERS-CoV infection. Results: A total of 10 papers were retrieved and included in the final analysis and review. The extent of asymptomatic MERS infection had increased with change in the policy of testing asymptomatic contacts. In early cases in April 2012-October 2013, 12.5% were asymptomatic among 144 PCR laboratory-confirmed MERS-CoV cases while in 2014 the proportion rose to 25.1% among 255 confirmed cases. The proportion of asymptomatic cases reported among pediatric confirmed MERS-CoV cases were higher (41.9%-81.8%). Overall, the detection rate of MERS infection among asymptomatic contacts was 1-3.9% in studies included in this review. Asymptomatic individuals were less likely to have underlying condition compared to fatal cases. Of particular interest is that most of the identified pediatric cases were asymptomatic with no clear explanation. Conclusions: The proportion of asymptomatic MERS cases were detected with increasing frequency as the disease progressed overtime. Those patients were less likely to have comorbid disease and may contribute to the transmission of the virus.