State of Knowledge and Data Gaps of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in Humans

Abstract

Background: Between September 2012 and 22 October 2013, 144 laboratory-confirmed and 17 probable MERS-CoV cases from nine countries were notified to WHO.

Methods: We summarize what is known about the epidemiology, virology, phylogeny and emergence of MERS-CoV to inform public health policies.

Results: The median age of patients (n=161) was 50 years (range 14 months to 94 years), 64.5% were male and 63.4% experienced severe respiratory disease. 76.0% of patients were reported to have ≥1 underlying medical condition and fatal cases, compared to recovered or asymptomatic cases were more likely to have an underlying condition (86.8% vs. 42.4%, p<0.001). Analysis of genetic sequence data suggests multiple independent introductions into human populations and modelled estimates using epidemiologic and genetic data suggest R0 is <1, though the upper range of estimates may exceed 1. Index/sporadic cases (cases with no epidemiologic-link to other cases) were more likely to be older (median 59.0 years vs. 43.0 years, p<0.001) compared to secondary cases, although these proportions have declined over time. 80.9% vs. 67.2% of index/sporadic and secondary cases, respectively, reported ≥1 underlying condition. Clinical presentation ranges from asymptomatic to severe pneumonia with acute respiratory distress syndrome and multi-organ failure. Nearly all symptomatic patients presented with respiratory symptoms and 1/3 of patients also had gastrointestinal symptoms.

Conclusions: Sustained human-to-human transmission of MERS-CoV has not been observed. Outbreaks have been extinguished without overly aggressive isolation and quarantine suggesting that transmission of virus may be stopped with implementation of appropriate infection control measures.

a) Country of probable exposure of laboratory-confirmed MERS-CoV cases b) Number of laboratory confirmed MERS-CoV cases by country of probable exposure

Bars do not represent the exact location of cases. The most detailed level of information for place was mapped when possible. For cases where only the province name was reported, the geographic centre of that province is mapped.

Epidemiologic Curve of MERS-CoV Confirmed (n=144) and Probable Cases (n=17)

*After week 24 in 2013, 58 cases were not reported with date for symptom onset. For these 58 cases, the symptom onset date was estimated (date of reporting to WHO minus median of difference between onset date and reporting date of those cases that had both of these dates available; the median difference was calculated by country). Cases are reported by the location where infection is believed to have occurred. Figure includes cases reported as of 22 October 2013.