Scientists said Wednesday they had found evidence that
SARS-like corona viruses can jump straight from a type of Chinese bat to humans
without the need for an intermediary animal "host".
The find has "enormous implications" for public
health control, with potentially pandemic viruses present, right now, in bats
in China that could cause another outbreak, said the authors of the study
published in the journal Nature.
"Even worse, we don't know how lethal these viruses
would be if such an outbreak erupted," co-author Peter Daszak of the Eco-Health
Alliance, a New York-based research group, said in a statement.
The Middle East Respiratory Syndrome Corona virus
(MERS-CoV) which first appeared in September 2012 and has claimed 62 lives
worldwide, is also believed to originate in bats – in Saudi Arabia. Corona
viruses are a large family of viruses that cause an array of human illnesses –
everything from the common cold to SARS. They also cause a number of animal
Origin in bats
Bats have long been thought to be the origin of the Severe
Acute Respiratory Syndrome corona virus (SARS-CoV) outbreak that killed
hundreds of people in Asia 10 years ago, but other SARS-like viruses found in
bats lacked the genetic ability to "bind" to human cells for
SARS had also been found in civet cats in wildlife markets
in China, and many scientists believed they were a necessary intermediary host
for the bat virus to mutate into a form able to target humans.
"Our current paper shows that this isn't necessary –
we have found SARS-like corona-viruses in Chinese horseshoe bats that are much
more closely related to human SARS and that can use the human cell
receptor," Daszak told AFP by email.
"That means they could emerge directly from bats to
people anywhere there is contact with this species of Chinese bat, not just in
the wildlife markets where civets are also found."
A receptor is a molecule on the surface of a human cell
that receives chemical signals via a spike protein on the surface of a virus –
a kind of lock and key mechanism. But not all viruses have the key to unlock
just any cell.
The study authors said their findings constituted the
strongest evidence yet that SARS itself may have originated in bats.
"I think it's the most likely hypothesis for how SARS
emerged – that bats carrying viruses similar to our new CoVs were in the
market, and infected both civets and people at the same time," said
The results underlined the importance of continued
surveillance of viruses in bats to pre-emptively identify ones that could cross
species, said the research team from China, Australia, Singapore and the United
"It is not uncommon for bats to be a food source for
many people in China and other parts of Asia, so the risk is substantial,"
said an Eco-Health Alliance statement.
Bats used in Chinese medicine
"Our work shows that bats are important reservoirs of
a number of viruses including MERS and we should be more careful about how we
interact with bats – let's give them the natural space for their habitat,
conserve them, and avoid hunting and trading in bats – this is good for
conservation and good for our health," said Daszak.
The results published in Nature were based on a genetic
analysis of virus samples taken over the course of a year from members of a
horseshoe bat colony in the south-western Chinese city of Kunming.
Daszak said the team had managed to isolate and cultivate
one of the viruses live in the laboratory, which will be used to work on a possible
The biggest threat
"The biggest threat for a pandemic now is not SARS
itself because that outbreak happened and ended. The biggest threat is for
something similar to SARS to emerge from wildlife and start off a new SARS-like
pandemic," he said.
Commenting on the study, Sanjaya Senanayake, associate
professor of medicine at the Australian National University, said the chances
of direct disease transmission from animals to humans increased as we encroach
further into their natural habitats.
"Of the 40 or so new infections in humans discovered
in the last 40 years, most have come from animals," Senanayake said.
"This increasingly intricate cohabitation becomes a
long-term issue for pandemic planners."
Picture: Bat from Shutterstock