As human cases rise in a mysterious viral outbreak that originated in China, scientists are rushing to identify the animals, where they suspect the epidemic began. In a controversial study published last night, a team of researchers in China claimed to have an answer: snakes.

But other scientists say there is no proof that viruses such as those behind the outbreak can infect species other than mammals and birds. “Nothing supports snakes being involved,” says David Robertson, a virologist at the University of Glasgow, UK.
The pathogen responsible for the outbreak belongs to a large family called coronaviruses, which includes the viruses that cause severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), as well as those behind the common cold. The latest virus — currently known as 2019-nCoV — is most closely related to SARS and related viruses that circulate in bats. But these can also infect other animals that can pass the virus to humans. Many scientists suspect that an unknown animal carrying 2019-nCoV spread the virus to humans at a live seafood and wild animal market in Wuhan, where the first cases were documented in December.

“The intermediate host is the missing piece of the puzzle: how have all these people got infected?” says Robertson.