Challenges ahead as the search for Covid-19's origin begins

Where did it come from? How did it spread? Can it be linked to the consumption of bushmeat? When exactly did the contagious virus jump onto humans? Is there a possibility that someone made it in a lab from where it escaped?  

The Covid-19 or SARS-CoV-2 has killed more than 1.6 million people, left millions more jobless and confined families to their homes. Yet, the world is unsure about the origins of the pathogen. 

Researchers agree the virus is zoonotic, which means humans contracted it from an animal. 

A team of World Health Organisation (WHO) experts is traveling to China next month. Its field investigation covers Wuhan, the city where the first cases of a pneumonia-like illness were first reported a year back. 

Linking together the chain of events that brought the virus from the animal kingdom to cities is crucial to avoid future outbreaks. But the process is not easy especially if it involves wild animals. 

“Tracking a disease in the wild can be challenging. An animal carcass needs to be fresh enough to isolate the pathogen,” says Dr. Prayag H S, a veterinarian from the Indian state of Karnataka, who researches big cats in their natural habitat. 

“In most cases what happens is that when we go to the spot, the animal is almost in a decomposing state. The terrain and the fact that at times large areas have to be covered, retrieving the body is difficult.” 

Not enough hints

A coronavirus, which matches a 96.2 percent sequence homology with SARS-CoV-2, has been identified in bats in Yunnan province of China. 

The way a zoonotic disease normally transmits is that it jumps from a reservoir animal to an intermediary species, which then spreads it to humans. Bats are known to be reservoirs of different viruses including the Hendra virus that killed horses and people in Australia in 1994. 

But a specific reservoir of SARS-CoV-2 is yet to be identified and the route of transmission remains a mystery even though scientists have found traces of the new coronavirus in cats, ferrets, hamsters, minks and other animal species. 

A live virus, and not just antibodies, needs to be extracted from a bat to prove that indeed it is the reservoir. 

Two-thirds of all infectious diseases in humans come from animals and three-quarters of all those are from the wildlife. The source of some of the most lethal zoonotic diseases continue to elude researchers. 

Epidemiologists spent four decades collecting and testing samples from mammals, birds and reptiles, yet they have been unable to find the source of the deadly Ebola virus.

The animal reservoir behind the outbreak of Severe Acute Respiratory Syndrome (SARS), just like Ebola, is still unknown, according to the WHO.

In the ten-member WHO team heading to China are scientists who have previously worked on identifying sources of other viruses. Dr Marion Koopmans, a virologist from the Netherlands, helped establish that dromedary camels were an intermediate host for the virus that causes MERS, another type of coronavirus. 

The WHO says Wuhan might have reported the first cases, but that doesn't necessarily mean the virus couldn’t have first surfaced elsewhere. 

Some countries identified cases of Covid-19 weeks before the first one was officially notified, and unpublished reports of positive sewage samples could suggest that the virus may have circulated undetected for some time, it says. 

The denials

The outgoing US President Donald Trump has repeatedly blamed China for the spread of Covid-19 by delaying the release of information after the virus outbreak. Beijing denies dragging its feet on the issue. 

China is also wary of the WHO’s focus on Wuhan. Earlier this month, state-owned Global Times ran stories which said the virus may have originated elsewhere. 

The geopolitics and the fact that multiple vaccines have hit the market have overshadowed the debate over Covid-19’s origin. 

Experts say it is important to figure out how the virus made its way to humans to prepare for future outbreaks. 

Infectious zoonotic diseases such as Covid-19, which spread from human to human, like wildfire, are very rare.

For instance, rabies, caused by an animal bite, is very lethal but it doesn’t get passed on. Ebola, HIV, SARS, MERS and now Covid-19 are just a handful of examples where viruses have spread due to human interaction. HIV started as a zoonosis, but later mutated into a human only strain.

What’s alarming is that these infectious outbreaks have emerged one after another for the past 40 to 50 years - pathogens which have lived in the animal kingdom for thousands of years are only now spilling over to humans.

“Why is that? This is a million dollar question,” says Prayag. 

“But I do believe that If you follow nature's law, nothing goes wrong. I think at some point in time we became greedy. Humans have cut trees and destroyed the ecosystem. Now nature is telling us, ‘Look you are not the boss, I’m the boss’.”