The Emergence of Human Coronavirus EMC: How Scared Should We Be?

Chan, Renee W. Y.; Poon, Leo L. M.

The SARS event has led to intense scientific interest in coronaviruses and to the discovery of many other novel coronaviruses in humans and animals. With these intense efforts, a great diversity of alphacoronaviruses and betacoronaviruses has been detected in bats (Fig. 1) . These findings suggest that bats might be the natural reservoirs of these two viral genera and that some of the bat coronaviruses might have adapted to other mammals in occasional spillover events in the past. Although the natural host for HCoV-EMC is yet to be identified, it is tempting to speculate that HCoV-EMC is of bat origin. In fact, recent bat coronavirus surveillance studies have indicated that a bat coronavirus (e.g., BtCoV/ VM314/2008) which is genetically closely related to HCoV-EMC can be detected in different countries in Europe (12) . But the sequence of this group of bat coronaviruses is still quite distinct from that of HCoV-EMC. This suggests that HCoV-EMC might be carried by an unknown bat species. Notably, bat coronaviruses that are genetically related to HCoV-EMC are all detected from Pipistrellus or Tylonycteris bats (Fig. 1) . Comprehensive virus surveillance of bats from these genera and others in the Middle East should be of top priority. Given the fact that SARS-CoV spread to humans via an intermediate host (civet cat) (13), other animals (e.g., poultry, pets, and game animals) that have frequent contacts with humans should also be tested. Assuming that the confirmed human cases/clusters were caused by multiple introductions of HCoV-EMC from animals to humans, identifying the source of this novel pathogen is still the key to preventing further spillover events.