A new analysis suggested that an outbreak of a deadly pig disease may have set the stage for Covid-19 to settle in humans. African swine fever (FSA), which hit China for the first time in 2018, interrupted the supply of pork, increasing the potential for human-virus contact as people looked for alternative meats.
Pork is the main source of meat in the Chinese diet, and the country produces half of the world’s pigs, which generate about 55 million tons of pork annually, forming an industry worth more than $ 128 billion (£ 98 billion). The ASF outbreak spread to most of China in the fourth quarter of 2019. The disease is intractable and incurable. Once this happens, the only solution is to kill the infected animals.
The dramatic drop in the supply of pork, following restrictions on the movement and slaughter of pigs led to price increases, increased the demand for alternative sources of meat for transportation across the country. These sources included wild animals, thereby greatly increasing opportunities for human-coronavirus contact, a team of researchers from China and the United Kingdom suggested in an analysis yet to be reviewed by peers.
“If more wildlife enters the human food chain, whether through [individuals] hunt … or go to the market and get different sources of meat. If that increases, it may just increase the opportunity for contact, ”said study author David Robertson, professor of viral genomics and bioinformatics at the University of Glasgow. “You are just increasing the opportunity for [Sars-CoV-2] viruses to enter humans. “
The key to preventing another future zoonotic pandemic is the Herculean task of finding out how it happened. Disease detectives, including a team from the World Health Organization, are still following the trail, but many suspect that Sars-CoV-2 probably originated in bats and spread to humans, possibly through an intermediate animal.
The first group of Covid-19 cases was detected in Wuhan, but it is possible that the disease originated elsewhere. In January 2020, Chinese scientists released the genetic sequence of the virus that came to be called Sars-CoV-2. Since then, scientists have shown that the virus probably had at least its distant ancestry in horseshoe bats in the Chinese province of Yunnan.
From a sample of 41 confirmed cases of Covid-19, 70% of those infected were stall owners, employees or regular customers of the Huanan market, which sold seafood, but also live animals, often caught illegally in the wild and slaughtered in the wild. in front of customers. But the first confirmed case had no apparent connection to the market.
The newly published analysis, which implies that ASF is the driver of the overflow of Sars-CoV-2 to humans, provided a likely explanation of what happened, Robertson said, noting that ASF could have caused a shortage of about 40 -60% of the total pig population, causing major disruption in the country’s meat industry.
“And that potentially explains why there is no direct connection [to the market in previous research], why we are finding it difficult to find the connection, ”he said. “Because with that kind of overflow, you would go to the market and expect to find infected animals yet – and it didn’t. And then, there is a puzzle, a kind of missing link.
At the moment, the idea that the shortage of pork led to the spillage of Sars-CoV-2 in humans was only a hypothesis, he added. “We are showing interruptions … imagine a wall, it is just a brick in that wall of evidence. It is something that we think should be considered in understanding what has unfolded.
“As usually happens in this type of investigation – it can take many years to unravel the probable routes. [While] it is unlikely that we will ever know exactly what happened – it seems likely that we will find a virus near a bat’s Sars-CoV-2, [or] maybe another species, ”he added.
“And then, from that, you can start saying, well, how did it get into humans?”
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