Since the respiratory disease emerged in central China in late December, health officials have raced to locate where and how the virus was first transmitted from its animal host to humans. It is however believed that a now-closed Wuhan city wholesale market played a role in the outbreak.
The key work of tracing the
animal transmission source of the COVID-19 coronavirus infection in humans is
ongoing and must be carried out to prevent future health emergencies, according
to a senior WHO scientist Dr Peter Embarek.
Since the respiratory disease
emerged in central China in late December, health officials have raced to
locate where and how the virus was first transmitted from its animal host to
humans. It is however believed that a now-closed Wuhan city wholesale market played
a role in the outbreak.
Dr Embarek, the Food Safety and
Zoonosis Expert at the World Health Organisation, says that remains unclear if
the seafood market in Wuhan was the original source for the virus which has so
far affected more the 3.5 million people and resulted in 250,000 deaths
“All these preliminary studies
and interviews and collection of data and so on will help pinpoint both in time
and in geographic terms where to look for the source,” Dr Embarek said in a
video conference with Journalists.
In the previous coronavirus
outbreaks, such as the MERS episode in 2012, finding the missing animal-human
link has been far from straightforward, even though everybody was looking for
the source, Dr Embarek explained.
In the end, it took months of
epidemiological detective work and a slice of luck before the transmission link
to camels was found, after health officials in Qatar reported two suspect cases
linked to a farm, which were followed to confirm the link to the dromedaries.
For scientists, getting the
original virus before it adapted to humans under a microscope could help to
unlock genetic secrets that could help protect future generations, the WHO
Concerning the transmissibility
of infection by animals that regularly come into contact with humans, he noted
that cats were susceptible to the virus and can also transmit the disease to
other cats. Ferrets have also been infected along with dogs to some extent,
while pigs and poultry seem to have greater resistance to the disease. He also
said that the new coronavirus could not be transmitted by mosquitos and
“There has been discussion about
mosquitos and whether other animals could transmit the virus and that’s not the
case”, Dr Embarek said. “These viruses have very specific affinities to certain
animal species and again to their ability to attach and infect specific cells
of different species. They cannot at all invade and infect particular animal
He highlighted the fact that many
people showed few or no symptoms of infection with COVID-19, likely
contributing to the outbreak’s rapid spread.
“We’ve learned a lot about the disease and we
know that the vast majority of cases have no or mild symptoms, so it would not
be surprising if, at that time, there were a lot of mild cases that were
undetected, because we didn’t even know they were mild cases. And that could
explain how some of the people who had no link with the market could have been