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Scientists Reinforce Search for Animal Link to Human COVID-19 Infections

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 globally. 

“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 official continued. 

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 parasites.

“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 species.” 

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 infected.”  

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