Bats are the potential source of coronavirus, new research suggests.
However, scientists stress the animal source of the recent outbreak in China has not been confirmed.
Identification and characterisation of the new virus reveals similarities with severe acute respiratory syndrome (Sars) coronaviruses.
Researchers analysed samples from seven patients with severe pneumonia, six of whom were identified as workers from the seafood market in Wuhan.
They found that full-length genome sequences – which determined the DNA of the virus – from five of the patients were almost (over 99.9%) identical to each other.
They also shared 79.5% sequence identity with Sars coronaviruses.
According to the study published in Nature, the virus sequence is 96% identical to a bat coronavirus, suggesting bats are a probable source of this coronavirus.
This comes as photos and video emerged of "bat soup" being consumed in China.
Reports suggest no bats were sold at the food market where the outbreak is believed to have originated.
This indicates the virus may have spread through another animal– yet to be identified – acting as an intermediate host between bats and humans.
The virus can spread from humans coming into contact with infected animals.
It is unlikely to survive in animals that have died, experts say.
Scientists also found the new virus, named 2019-nCoV, enters cells through the same route as Sars coronaviruses.
Antibodies isolated from patients infected with the new strain are shown to have the potential to neutralise the virus.
Zheng-Li Shi, a virologist and researcher at the Wuhan Institute of Virology, and colleagues developed a test that can differentiate 2019-nCoV from all other human coronaviruses.
They found that while it was detected in initial oral swab samples, subsequent samples taken about 10 days later did not have a positive viral result.
This suggests the most likely route of transmission is through the airways of individuals.
Dr Michael Skinner, reader in virology at Imperial College London, said: "The discovery definitely places the origin of nCoV in bats in China.
"We still do not know whether another species served as an intermediate host to amplify the virus, and possibly even to bring it to the market, nor what species that host might have been."
In a separate study, researchers studied a 41-year-old male market worker admitted to a hospital in Wuhan on December 26 2019, who experienced symptoms of respiratory illness, including fever, chest tightness and a cough.
In a sample of fluid taken from his lung, they identified a novel virus and found that the viral genome shared 89.1% similarity with Sars-like coronaviruses from bats.
But the researchers say it is not possible to conclude from the analysis of a single patient that this coronavirus is the cause of the current outbreak.
Diana Bell, Professor of Conservation Biology at the University of East Anglia, said she is not convinced bats are to blame.
She said information she had received suggested there were no bats in the market and that at this time of year they would not be flying around.
Prof Bell explained that it was dangerous to point the finger at bats and stop looking for alternative sources, without having looked at all other possible sources.
She said: "I will only be convinced that bats are the source once other factors have also been extensively studied.
"I think it is important to keep an open mind."