A new strain of coronavirus that emerged in China may have originated in bats or snakes, according to genetic analysis of the virus that has so far killed 17 people.
The theories are based on examination of the genome sequence of the virus released by authorities in the wake of the outbreak, with two studies pointing to the likely role of bats in the outbreak.
One study, published Tuesday in the journal Science China Life Sciences, which is sponsored by Beijing’s Chinese Academy of Sciences, looked at the relations between the new strain and other viruses.
It found the coronavirus that emerged from China’s Wuhan was closely related to a strain that exists in bats.
“Bats being the native host of the Wuhan CoV [coronavirus] would be the logical and convenient reasoning, though it remains likely there was intermediate host(s) in the transmission cascade from bats to humans,” the researchers from several institutions in China wrote in the paper.
That study did not speculate about which animal could have been an “intermediate host,” but a second study published Wednesday in the Journal of Medical Virology identifies snakes as the possible culprit.
“To search for (a) potential virus reservoir, we have carried out a comprehensive sequence analysis and comparison. Results from our analysis suggest that snake is the most probable wildlife animal reservoir,” the paper says.
The researchers caution that their conclusions require “further validation by experimental studies in animal models.”
Neither study explained how the virus may have been transmitted from animals to humans.
But they could offer clues to Chinese authorities as they hunt for the source of the outbreak that has sickened hundreds of people in the country and has been confirmed as far afield as the United States.
The food market where the deadly virus surfaced offered a range of exotic wildlife for sale, including live foxes, crocodiles, wolf puppies, giant salamanders, snakes, rats, peacocks, porcupines, camel meat and other game.
Gao Fu, director of the Chinese center for disease control and prevention, said in Beijing on Wednesday that authorities believe the virus likely came from “wild animals at the seafood market” though the exact source remains undetermined.
Severe Acute Respiratory Syndrome, or SARS, was linked to Chinese consumption of civet meat.
Many exotic species are still widely consumed in China or other Asian countries where they are considered a delicacy—like the civet or some rats or bats—or for purported health benefits unproven by science.
As China locks down the city at the epicenter of a new viral outbreak, countries around the world are scrambling to prevent the spread of the deadly disease.
While most patients are in Wuhan, cases have been detected across China and a few abroad.
Nathalie MacDermott of King’s College London said it seems likely the virus is spreading through droplets in the air from sneezing or coughing.
Scientists at Imperial College London published an estimate on Wednesday that 4,000 people had been infected in Wuhan—around 10 times the official figure.
The symptoms appear to be less aggressive than those of the virus that spread in 2002 and 2003.
However, Antoine Flahault, director of the Institute of Global Health at the University of Geneva, said the fact that the virus seems milder in the majority of people is “paradoxically more worrying” as it allows many to travel further before their symptoms are detected.
The 17 patients who died were between 48 and 89 years old. Most had underlying health issues including cirrhosis, diabetes, high blood pressure or coronary heart disease, China’s National Health Commission said.
Fears of a bigger epidemic have risen as hundreds of millions of people travel across the country for China’s Lunar New Year holiday, which starts Friday.
Authorities halted flights and trains out of Wuhan from Thursday and told people in the city they should not leave without a special reason.
In Thailand, officials have introduced mandatory thermal scans of passengers arriving at airports in Bangkok, Chiang Mai, Phuket, and Krabi from high-risk areas in China.
In Hong Kong, authorities have said they are on high alert, carrying out scans at the city’s airport—one of the world’s busiest—and at other international land and sea crossing points. High-speed rail tickets to Wuhan are no longer being sold while airliner Cathay has said it will stop flights to the city until 29 February.
Taiwan has issued travel advisories and went to its second-highest alert level for Wuhan, recommending against all travel to the city.
South Korea urged its citizens on Thursday not to travel to Wuhan, with the foreign ministry telling anyone intending to visit the area to “please carefully review the necessity of the trip.”
The US has also ordered the screening of passengers arriving on direct or connecting flights from Wuhan, including at airports in New York, San Francisco, and Los Angeles.
In Europe, Britain and Italy introduced enhanced monitoring of flights from Wuhan, while Romania and Russia are also strengthening checks.