Coronavirus Update: Did The Deadly Disease Originate In Bats?

The new coronavirus in China has killed at least 170 people, infected 7,000 others and now has spread to other parts of the world. As scientists and physicians seek to find its source, a new study published by the British medical journal Lancet suggests the disease may have originated in wild bats.

Researchers studied 10 genome sequences of the novel coronavirus – which is now called “2019-nCoV” in scientific circles -- from nine infected patients in China. They found that all the genome sequences were virtually the same, sharing more than 99.98% of the same genetic sequence.

This suggested that the virus reached humans very recently.

"It is striking that the sequences of 2019-nCoV described here from different patients were almost identical," said study co-lead author Weifeng Shi, a professor at the Key Laboratory of Etiology and Epidemiology of Emerging Infectious Diseases in Universities of Shandong Province. "This finding suggests that 2019-nCoV originated from one source within a very short period and was detected relatively rapidly."

The researchers then compared the 2019-nCoV genetic sequence with others and discovered that the most closely similar viruses were two coronaviruses that originated in bats.

“These data are consistent with a bat reservoir for coronaviruses in general and 2019-nCoV in particular,” said study co-author Professor Guizhen Wu of the Chinese Center for Disease Control and Prevention.

Indeed, many of the first cases of the virus in Wuhan, China were people who either worked at or shopped at the Huanan seafood market, where many wild animals are offered for sale. (Eight of the patients from the Lancet study visited the Huanan seafood market, while the other stayed in a hotel near the market).

However, bats have not been sold in that market in recent times. Hence, the Lancet researchers suspect that although the virus probably originated in bats, the disease was first spread to humans by another unknown infected animal. One possibility might be snakes, which were sold at the seafood market (and which are known to hunt and eat bats) – but it remains unclear if snakes can be infected by coronaviruses.

"However, despite the importance of bats, it seems likely that another animal host is acting as an intermediate host between bats and humans," said Wu.

The recent outbreak "again highlights the hidden virus reservoir in wild animals and their potential to occasionally spill over into human populations," the authors wrote.

Coronaviruses can affect many different animals, including camels, cattle, cats, and bats, said the Centers for Disease Control and Prevention. In some rare cases, these viruses can pass from animals to humans. In a food market where humans come in close contact with live and dead wild animals, a virus can easily be transmitted from animals to humans.

Indeed, the severe acute respiratory syndrome, or SARS coronavirus, which killed nearly 800 people 2003-2004, moved from bats to civets, a small cat-like creature, to humans.

"Bats and birds are considered reservoir species for viruses with pandemic potential," said Bart Haagmans, a virologist at the Erasmus Medical Center in Rotterdam, Netherlands.

Bats are believed to be the source of at least three other recent pandemics: Ebola, which has killed 13,500 people since 1976; Middle Eastern respiratory syndrome, or MERS; and the Nipah virus, which has a fatality rate of 78%.

"We know a fair amount of viruses on the World Health Organization's Blueprint list of priority diseases have either a direct or indirect link with bats," said Vincent Munster, a scientist at Rocky Mountain Laboratories in Montana.

The seafood market in Wuhan where the virus is believed to have originated has since been disinfected and shut down by local authorities.

"For cultural reasons in the region, people want to see the specific animals they're buying be slaughtered in front of them, so they know they're receiving the products they paid for," Emily Langdon, an infectious disease specialist at the University of Chicago, wrote in an article. "That means there's a lot of skinning of dead animals in front of shoppers and, as a result, aerosolizing of all sorts of things."

Christian Walzer, the executive director of the Wildlife Conservation Society's health program, said it’s time to close all markets that trade in live animals.

"Poorly regulated live-animal markets mixed with illegal wildlife trade offer a unique opportunity for viruses to spill over from wildlife hosts into the human population," the Wildlife Conservation Society said in a statement.