Holmes added that he is unsure whether the Wuhan CDC ramped up disease surveillance or introduced new safety measures in the years preceding the pandemic, and the China CDC has not responded.
The Huanan market gained global notoriety when the first cases of COVID-19 (initially reported as a “mystery pneumonia” on December 31, 2019) were found in people who worked and shopped there.
Of the initial 41 people hospitalised with pneumonia who were officially identified as having COVID, two-thirds were exposed to the market, which was closed and sealed off by the Wuhan authorities on January 1, 2020.
Experts believe the site played a significant role in the initial circulation of COVID-19, either as the site of the initial “spillover” event where an animal virus jumps to humans, or as an “amplifier” of the early epidemic.
A report from the World Health Organisation (WHO) on the origins of Sars-CoV-2 provided crucial details. Though it said “no firm conclusion” could be drawn on the precise role of Huanan market, it found the virus most likely jumped from bats to humans via an as-yet-unknown animal.
The wildlife trade in general, and wet markets in particular, have long been linked to the emergence of new pathogens. There is evidence SARS jumped to humans at markets in Guangdong, China in 2002 and data points to similarly a significant role in 2019.
In early 2020 Chinese researchers collected close to 1,000 samples from Huanan market – swabbing everything from rubbish bins, doors and stalls to stray cats and mice – and found widespread contamination “compatible with introduction of the virus through infected people, infected animals or contaminated products”.
Meanwhile, of the first 168 COVID-19 cases, roughly a third had a connection to Huanan market. Genome sequences from some of those in this group found eight of the earliest samples were identical, confirming there was an outbreak there.
Yet the first person with a known link to Huanan market became ill on December 12, four days after the first known case. This suggests COVID-19 may have been spreading under the radar in several parts of Wuhan simultaneously before Huanan market amplified circulation.
The joint WHO-China team also found no evidence that live wildlife was still sold at the market – though noted that both Holmes’ pictures and “unverified photographs and videos in media reports” suggest otherwise – and none of 457 animal samples taken from the market between January and March 2020 tested positive for Sars-Cov-2.
The report added: “The manager informed the teams the market was cleaned twice a day, morning and evening. Pests and rats are sought out and killed; holes were closed. Rigorous cleaning was done once or twice a week. Even though there are rooms above some stalls, vendors were not allowed to live in the market.”
But Holmes and others, including members of the WHO team, believe more samples need to be taken to “follow the animals”, and caution that finding wildlife involve in the early transmission chain is like finding a needle in a haystack.
It is also possible that the virus was introduced to the market by an already infected person involved in earlier stages of the wildlife trade.
“We know how easily Sars-Cov-2 spread from minks to mink farmers in Europe,” said Dr Dale Fisher, an expert in infectious diseases and chair of the Global Outbreak Alert and Response Network. “So it’s likely this could happen on a farm, and the farmer was the index case who then took it to the market, where there was a super-spreading event.
“But evidence points towards wildlife. And whether it’s been plague on rats, or Ebola on bats and primates, or SARS-1 on civet cats and bats, camels for MERS – historically these outbreaks all had species jumps and then amplification events,” he said.
It is estimated that birds and mammals harbour roughly 700,000 viruses with the potential to jump to people, while 70 per cent of new emerging infectious diseases come from wild animals. Places where numerous species mix in close quarters with humans, with few biosecurity measures in place, are high risk.
Just this week, the WHO issued new guidance urging countries to crack down on wet markets and suspend the sale of captured live wild animals as an “emergency measure” to protect public health.
“In my mind, the wildlife trade is the most likely source of it. The role of that market is still uncertain, but there was clearly a lot of transmission and to me it smells like there’s a strong link – we need to follow it through,” Holmes said.
“My concern is that the finger pointing has got so bad, will that happen? I think China just doesn’t want it to be China… so then the question is, are we actually going to see all the data? I honestly don’t know. But the more the politics gets into it, the less likely we will.”
The Telegraph, London