Since the new coronavirus emerged little over a month ago, experts have wondered where it came from and how deadly it could be.
The first human to have caught the virus is thought to have done so at a seafood and live animal market in the Chinese city of Wuhan, capital of Hubei province.
Of the six coronavirus strains previously known to infect humans, the new one initially appeared most genetically similar to severe acute respiratory syndrome (Sars), which killed 774 people during its 2004 outbreak.
Scientists from Fudan University in Shanghai have since found it appears to be 89.1% genetically similar to “a group of Sars-like coronaviruses”.
With Sars having started in bats, this suggests the nocturnal creatures may also be responsible for the new coronavirus, which has killed at least 361 people in China so far.
Authorities have confirmed 17,485 cases of the new coronavirus in mainland China alone, according to John Hopkins University.
The Lancet journal has reported, however, that 75,000 people could have battled the infection just in Wuhan.
Most of those who initially became ill worked at or visited the market, which was promptly shut.
The Fudan scientists analysed one of the workers, a 41-year-old man who was admitted to hospital on 26 December after battling a fever, tight chest and cough for a week.
A “cluster” of patients were first reported to the World Health Organziation on 31 December.
A “lung sample” taken from the worker allowed the virus – called 2019-nCoV – to be genetically screened, revealing its similarity to Sars.
“The identification of multiple Sars-like-coronaviruses in bats led to the idea these animals act as the natural reservoir hosts of these viruses,” the scientists wrote in the journal Nature.
A team from the Chinese Academy of Sciences in Wuhan also analysed the viral DNA of five coronavirus patients.
They found the new strain seems to share 79.5% of its genetics with Sars.
Results, also published in Nature, further show the virus is 96% “identical” to a coronavirus that infects bats.
“These two scientific papers provide the formal evidence for what is already widely known,” said Professor Ian Jones of the University of Reading.
“2019-nCoV is a bat virus and Sars is the closest relative seen previously in people.
“In essence, it’s a version of Sars that spreads more easily but causes less damage.
“The virus also uses the same receptor, the door used to get into human cells, which explains transmission and why it causes pneumonia.
“Most encouragingly though, this indicates treatments and vaccines developed for Sars should work for the Wuhan virus.”
Scientists from Peking University in Beijing have previously traced 2019-nCoV to snakes, namely the Chinese krait and cobra.
They compared the DNA of the virus to that of other pathogens from various places and species.
Results suggested 2019-nCoV is a “combination of a coronavirus found in bats and another coronavirus of unknown origin”.
The virus is thought to contain a mix of proteins that bind to cell receptors, allowing it to enter and trigger disease.
The team found snakes that were likely the “intermediate host” between bats and humans, with the mix of proteins facilitating the species “jump”.
The masked palm civet, a mammal native to the Indian subcontinent and south-east Asia, was an intermediate host for Sars between bats and humans.
Another coronavirus strain is Middle East respiratory syndrome (Mers), which killed 858 during its 2012 outbreak.
Mers is also thought to have originated in bats, with camels being the intermediate host.
Not all experts are convinced by the role of snakes in 2019-nCoV’s outbreak, however.
Speaking when the Peking University results were released, Professor Paul Hunter of the University of East Anglia said: “It is still not known with certainty and it may never be definitively proved.
“There are initial, although contested, reports the virus has already been detected in both bats and snakes, and the strains in both bats and snakes are similar to each other, and to the strains from human cases.
“There is still much more to find out about the virus and there is a real possibility the exact origin may not be found.
“The big question is no longer where it came from, but how and where it is spreading in human populations.”
Coronaviruses are “RNA viruses”, which means they “mutate all the time”, Yahoo UK reported.
In simple terms, RNA is a “precursor” to the more well-known DNA.
Exposure to live animals at the market likely enabled the virus to “jump” from its origin species into humans.
Like all coronaviruses, the new strain initially causes flu-like symptoms.
China's National Health Commission confirmed the virus can spread person-to-person, via sneezing, coughing or shaking contaminated hands.
In the most severe cases, victims are succumbing to pneumonia.
This comes about when a respiratory infection causes the alveoli (air sacs) in the lungs to become inflamed and filled with fluid or pus, according to the American Lung Association.
The lungs then struggle to draw in air, resulting in reduced oxygen in the bloodstream.
“Without treatment the end is inevitable,” said the charity Médecins Sans Frontières.
“Deaths occurs because of asphyxiation.”
Pneumonia is usually caused by bacteria, which tend to respond to antibiotics.
When a virus is to blame, pneumonia may be treated via “antiviral medication”, according to the American Lung Association.
The US Centers for Disease Control and Prevention have warned there is no specific treatment for coronaviruses.
Professor Peter Horby from the University of Oxford added there is “no effective anti-viral” at the moment, with treatment being “supportive”.