A new coronavirus related to SARS has many potential hosts and could pass from animals to humans repeatedly, researchers in Germany said.
Lead author Christian Drosten of the University of Bonn Medical Centre in Germany said given the similarities, the researchers wanted to know whether the new coronavirus 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, 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 said 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 infecting others, Drosten added.
However, hCoV-EMC does not use the same receptor and the virus does not use ACE2, Drosten said.
Like SARS, hCoV-EMC is most closely related to coronaviruses from bats, but unlike SARS, this study found that hCoV-EMC can still infect cells from many different species of bats.
"This was a big surprise," say Drosten. "It's completely unusual for any coronavirus to be able to do that -- to go back to its original reservoir."
The virus is also able to infect cells from pigs, indicating that it uses a receptor structure that all these animals have in common. If that receptor is present in mucosal surfaces, such as the lining of the lung, it is possible the virus could pass from animals to humans and back again, making animals an ongoing source of the virus that would be difficult or impossible to eliminate, Drosten said.
The findings were published in mBio, the open-access journal of the American Society for Microbiology.