22 February 2013 - The recent implication of a new emerging human coronavirus (hCoV-EMC1) as the cause of a fatal respiratory disease in the Middle East and Europe emphasizes the importance of surveillance for coronaviruses (CoV), which have shown the potential to spill-over from an animal reservoir into the human population in recent years. To date, however, the hCoV-EMC has not been identified in other animal species.
As of 22 February 2013, WHO has reported of a total of 13 confirmed cases of human infection with hCoV-EMC, including seven deaths. These cases occurred in Jordan in April 2012, in Qatar in September 2012, in Saudi Arabia since November 2012 and in the United Kingdom (UK) in February 2013. To date, evidence of human-to-human transmission has been limited to workers in a hospital in Jordan and familial clusters in Saudi Arabia and the UK.
Coronaviruses have the largest genome of the RNA viruses and are characterized by their high mutation and recombination rates. They can infect a wide variety of mammals and birds, causing respiratory, enteric, hepatic, and neurological diseases. Many animal coronaviruses cause long-term or persistent enzootic infections. Long periods of coronavirus infection, combined with a rapid genetic evolution, increase the probability that a virus mutant, with an extended host range, might arise. On the basis of genotypic characteristics, coronaviruses are classified into four distinct groups: Alphacoronavirus (which infect porcine, canine, feline and human species), Betacoronavirus (which infect rodent, bovine, human, porcine, canine and equine species), Deltacoronavirus (which infect porcine, feline and avian species) and Gammacoronavirus (which infect domestic and wild birds species). Bats are the natural reservoir of all currently known coronavirus groups.
The hCoV-EMC is a Betacoronavirus and thus, is part of the group of viruses that cause Severe Acute Respiratory Syndrome (SARS), of which a global outbreak occurred in 2003 and 2004, infecting about 8 000 people (with 800 deaths) worldwide. However, the genetic sequence of the SARS virus belongs to a separate lineage than that of the hCoV-EMC sequence. As a consequence, the hCoV-EMC uses different cell receptors to cause infection than those used by the SARS-CoV. In addition, the hCoV-EMC retains its ability to infect human, bat and porcine cells. The latter result is remarkable, because coronaviruses, in general, show fairly strict host specificity, and raises questions of the hCoV-EMC’s adaptation to human and of its animal origin. The hypothetical ancestor comes likely from bats or from an unidentified intermediary host. The level of spread within the human population and the frequency of animal-to-human jumps remain unknown.
At this stage, FAO considers the hCoV-EMC disease as a human health issue. However, FAO encourages animal health services to work closely and coordinate with human health services in hCoV-EMC outbreak investigations and surveillance activities, to jointly investigate any potential link of confirmed hCoV-EMC cases with potentially infected animals. Countries conducting surveillance in bats species and other potential animal reservoirs are encouraged to share and communicate any relevant information on coronavirus circulation that may help improve the understanding of the ecology of emerging coronaviruses and potential risks for livestock and humans.