Wuhan-based virus scientist Shi Zhengli has identified dozens of deadly coronavirus strains in recent years. But they’re just the tip of a gigantic iceberg, she warns.
On December 30, while attending a conference in Shanghai, Shi Zhengli received a call from her boss. Mysterious samples of patients had just arrived at the Wuhan Institute of Virology, and according to initial analyzes, a new coronavirus was visibly beginning to spread in the region.
If the discovery is confirmed, and given the state of health of the first patients, this new pathogen could pose a serious threat to public health. “Give up everything you do and treat it now,” she recalls hearing over the phone.
Shi Zhengli, nicknamed the “bat woman” by her colleagues, therefore jumped on the first plane to go to Wuhan. What she didn’t know yet was that the mysterious disease caused by the virus had already spread like wildfire. But let’s back up a bit.
The SARS experience
Shi Zhengli has been studying bats carrying viruses for about 16 years. It all started in 2004, when part of the world had just suffered the infamous SARS epidemic. The researcher then joined an international team of researchers who aimed to collect samples from caves near Nanning, China.
These expeditions were of paramount importance since, before SARS, coronaviruses were best known for causing common colds. This epidemic has truly changed the situation. It was indeed the first time that a deadly coronavirus with pandemic potential appeared to emerge. So we had to go back to the source, find the culprit, in order to better understand this new danger that our species had to face.
Whenever Shi’s team located a bat cave, a net was placed at the opening before dusk. The idea was to capture small mammals venturing outside to feed overnight. After the bats were trapped, the researchers took blood and saliva samples, as well as fecal swabs.
Unfortunately, in eight months of field research, the researchers had not isolated any trace of genetic material from the coronavirus. The team was on the verge of giving up when a research group from a nearby laboratory finally gave them a diagnostic kit to test the antibodies produced by people with SARS.
Everything then accelerated. Researchers quickly identified three species of bats carrying famous antibodies. It was only then that they realized that the presence of coronavirus in bats was fleeting and seasonal, and not constant, but that the presence of antibodies could persist from a few weeks to several years.
The Shi team, armed with this new information, then continued field research to finally succeed in reducing the locations likely to shelter the bats responsible for the epidemic. They finally turned to Shitou Cave, found on the outskirts of Kunming, the capital of Yunnan. The analyzes that followed then confirmed that everything started from there.
It was a victory for the researchers, but these analyses also revealed other problems. In this cave, they have indeed discovered hundreds of additional coronaviruses. “The majority of them are harmless,” said Shi Zhengli. But dozens belong to the same group as SARS. ”
A proximity problem
For many, the wildlife markets in China – which sell a wide range of animals such as bats, civets or pangolins – are perfect viral crucibles. On February 24, the nation also permanently banned the trade and consumption of wildlife (except for research and medicinal purposes). But you have to understand that this is only part of the problem.
Near Shitou Cave, where many villages are located, the Shi team collected blood samples from more than 200 residents in 2015. Six of them (nearly 3%) were found to carry antibodies to SARS-type coronaviruses from bats. However, none had handled these animals, nor reported symptoms related to possible pneumonia.
So you don’t have to be a wild animal trader or consume it, to be infected.
And that is the problem. These inter-species relationships are unfortunately increasingly close with the increase of the human population which, inevitably, encroaches on the wildlife habitats. And if the reservoirs do indeed seem to be concentrated only in certain areas, remember that our world is now governed by international trade. Pathogens are therefore able to spread quickly, relying on airports as relay points.
Another problem also emerged in late 2016, when pigs from four farms in Qingyuan County, located a few kilometers from the site of the SARS outbreak, began to experience acute vomiting and diarrhea. Almost 25,000 animals ultimately had to be slaughtered.
Since local veterinarians had not been able to detect any known pathogenic agent, the virologist had to go there. It finally emerged that we owed this acute swine diarrhea syndrome (SADS) to a virus whose genomic sequence was 98% identical to a coronavirus found in a nearby cave.
And this is where it gets very dangerous. Because pigs and humans have a very similar immune system, which makes it easier for viruses to pass between the two species, on the one hand. But we must also take into account the scale of pig farming in the world, which involves frequent and close contact between humans and animals. This is why, according to the virologist, the search for new coronaviruses in pigs should be considered a top priority.
Meanwhile, in Wuhan, the “batwoman” continues to conduct research in this area. “What we discovered is just the tip of an iceberg,” she explains, estimating that there may be as many as 5,000 strains still to be discovered in bats around the world. “Coronaviruses will cause more epidemics. That’s why we have to find them before they find us. ”