The SARS epidemic of 2002-2003 was short-lived, but the new human coronavirus that is alarming public health authorities can infect cells from humans and bats alike, a fact that could make the animals a continuing source of infection, according to a study to be published in mBio today. The new coronavirus, called hCoV-EMC, is now blamed for five deaths and several other cases of severe disease originating in countries in the Middle East. According to the new results, hCoV-EMC uses a different receptor in the human body than the SARS virus, and can infect cells from a wide range of bat species and pigs, indicating there may be little to keep the virus from passing from animals to humans over and over again.
First identified in a patient in Saudi Arabia in June, nine laboratory-confirmed cases of hCoV-EMC infection have now been identified, five of whom have died. Although the virus does not apparently pass from person-to-person very readily, the case fatality rate and the fact that the source of the virus has not been identified have caused concern among global public health authorities. Cases of hCoV-EMC infection are marked by severe pneumonia and often by kidney failure. mBio published another study on the genome of hCoV-EMC that detailed its relatedness to other coronaviruses in November.
“This virus is closely related to the SARS virus, and looking at the clinical picture, it causes the same pattern of disease,” says Christian Drosten of the University of Bonn Medical Centre in German, a lead author of the study.
For SARS, the Receptor Determined the Course of the Epidemic
Given the similarities, Drosten and his colleagues wanted to know whether hCoV-EMC and SARS might use the same receptor, a sort of molecular “dock” on human cells that the virus latches onto to gain entry to the cell. The SARS receptor, called ACE2, is found mostly on pneumocytes deep within the human lung, so an individual must breathe in many, many SARS viruses for a sufficient number of them to reach this susceptible area and cause an infection. Drosten says this simple fact helped ensure the SARS outbreak didn’t spread like wildfire and was mostly limited to healthcare workers and residents of overcrowded housing in Hong Kong. Also, once a person was infected with SARS in the deep part of their lungs, he or she felt sick almost immediately and therefore was not active in the community and infecting others, another aspect of the receptor that helped curb the outbreak.
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