Pandemic Almost Didn’t Happen, New Genetic Study Says

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By Maggie Fox, CNN

(CNN) – The coronavirus pandemic has hardly happened, according to a new study.

Researchers working to show when and how the virus first appeared in China calculate that it likely didn’t infect the first human until at the earliest October 2019. And their models showed something else: it almost failed to become a pandemic virus.

Only bad luck and overcrowded conditions in the Huanan seafood market in Wuhan – where the pandemic appears to have started – gave the virus the advantage it needed to explode worldwide, the researchers reported in the journal. Science.

“It was a perfect storm – we now know it took a stroke of luck or two to establish itself firmly,” Michael Worobey, professor of evolutionary biology at the University of Ottawa, told CNN. Arizona who worked on the study.

“If things had been a little bit different, if that first person who brought this to the Huanan market had decided not to go that day, or even was too sick to go and stayed behind. home, that or some other early super-broadcast events may not have happened. We may never even have known. “

The team used molecular dating, using the rate of current mutations to calculate how long the virus has been around. They also ran computer models to show when and how it could have spread, and how it spread.

“Our study was designed to answer the question of how long could SARS-CoV-2 circulate in China before it was discovered,” said Joel Wertheim, associate professor in the Division of Infectious Diseases and of Global Public Health, University of California, San Diego School of Medicine.

“To answer this question, we combined three important pieces of information: a detailed understanding of how SARS-CoV-2 spread in Wuhan before the lockdown, the genetic diversity of the virus in China, and reports of the first cases. of COVID-19 in China. By combining this disparate evidence, we were able to set an upper limit in mid-October 2019 for when SARS-CoV-2 started circulating in Hubei province. “

The evidence strongly indicates that the virus could not have circulated before this, the researchers said. There have been reports from Italy and other European countries that the virus may have infected people there before October. But Thursday’s study says just a dozen people were infected between October and December, Worobey said.

“Given this, it is difficult to reconcile these low levels of the virus in China with allegations of infections in Europe and the United States at the same time,” Wertheim said in a statement. “I am quite skeptical of the COVID-19 allegations outside of China at this time. “

The study indicates that the virus appeared in China’s Hubei province and not elsewhere, the researchers said.

“Our results also refute the claims of a large number of patients requiring hospitalization due to COVID-19 in Hubei province before December 2019,” they wrote.

From a handful of “spitting” cases in late 2019, the virus has exploded around the world. According to Johns Hopkins University, it has been diagnosed in 121.7 million people and killed nearly 2.7 million. The United States is by far the most affected country, with nearly 30 million diagnosed cases and nearly 540,000 deaths.

The study does not show which animal caused the virus. Genetic evidence shows that bats carry a closely related virus and also suggests that another intermediate animal species may have been infected and transmitted the virus to a human somewhere.

It happens. The United States Centers for Disease Control and Prevention regularly tracks and reports cases of new strains of influenza infecting people who attend county fairs and interact with pigs, for example. But so far none of these infections have led to an epidemic or even an epidemic.

What is needed is an infected person and a lot of contact with other people, like in a densely packed seafood market. “If the virus is not lucky enough to find these circumstances, even a well-adapted virus can go away,” Worobey said.

“It gives you some perspective – these events are probably happening a lot more frequently than we think. They just don’t make it and we never hear about it, ”Worobey said.

And that could have happened with Covid-19.

In the models run by the team, the virus only takes off about 30% of the time. The rest of the time, models show it should have gone away after infecting a handful of people.

“What may have happened here is that the virus was spreading to a very small number of people in October, November and December, and then it entered this Huanan seafood market,” he said. declared Worobey.

It is likely that the market was not where the virus first infected people, but simply where it gained momentum.

Considering how short the virus was around, it’s remarkable that it was identified so quickly, Worobey said.

“It was clearly enough sometime in December before there was a large enough group of people infected that there was a chance of discovering a new virus,” he said. In January 2020, it had been sequenced and characterized.

Nonetheless, it was too late – perhaps because Covid-19 isn’t deadly enough. The first SARS virus killed nearly 10% of its victims from 2002 to 2004 before being stopped thanks to a concerted global effort.

“As a scientific community, we were certainly aware of the pandemic potential of a highly transmissible and moderately virulent pathogen. But our disease reporting system depends on detecting peak hospitalizations and deaths. Obviously, that wasn’t enough to stop Covid-19, ”Wertheim told CNN.

The-CNN-Wire
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