A lethal pig virus that shows similarities to Sars could jump to humans.
Porcine deltacoronavirus causes acute diarrhoea and vomiting in infected pigs and can be fatal.
New research suggests the pathogen readily jumps between the cells of different species, including humans.
First detected in China in 2012, it shares characteristics with Sars (severe acute respiratory syndrome) and Mers (Middle East respiratory syndrome).
Sars was responsible 774 deaths in 37 countries in 2002 and 2003, while an ongoing Mers outbreak in Saudi Arabia has so far led to more than 1,800 cases of infection and 708 associated deaths.
Concerns were first raised about porcine deltacoronavirus following an outbreak in the US in 2014.
The latest study, reported in the journal Proceedings of the National Academy of Sciences, shows how the virus targets a specific receptor molecule on the surface of cells lining the airways and digestive tract.
In laboratory tests the virus bound to the receptor not only in pigs, as expected, but also chickens, cats and humans.
Lead researcher Dr Scott Kenney, from Ohio State University’s Food Animal Health Research Programme, said: “A receptor is like a lock in the door.
“If the virus can pick the lock, it can get into the cell and potentially infect the host.
“From that point, it’s just a matter of whether it can replicate within the cells and cause disease in those animals and humans.”
So far there are no known cases of the virus in humans.