Scientists in China's Hong Kong said on Thursday they had identified the virus behind a mystery pneumonia.
The finding, confirmed by the US Centers for Disease Control and Prevention, will allow doctors to diagnose the disease in patients much faster, reducing the death rate.
The group of microbiologists from the University of Hong Kong identified it as a new strain from the family of coronaviruses, which are the second leading cause of colds in humans.
"It appears to us the coronavirus is the primary cause of the disease...it is possible of course that other viruses might also infect the same patient and might increase the severity of the disease," scientist Malik Peirius told a news conference.
Peirius said the culprit behind the disease, which has infected more than 1,300 people around the world, was a new strain that may have originated from an animal virus.
But it was unlike any known human or animal virus.
The Hong Kong team also said they had developed a diagnostic test that would allow doctors to tell within eight hours if anyone was suffering from the disease.
Peirius said the infection was spread through coughing and sneezing, but also by touching droplets from infected people, which can carry an active virus for around three hours. Keeping hands clean was therefore an important precaution, he said.
Chances of recovery should be about 90 percent, if the victim was not suffering another dangerous disease, and was treated early. Victims were responding well to a cocktail of anti-viral drugs and steroids, the team added.