Article by Lalita Panicker, Consulting Editor, Views, Hindustan Times, New Delhi

Test and sample virus crown covid virus 19. COVID-19 tests illustration. Image credit: ambrozinio / 123rf

Image credit: ambrozinio / 123rf

Scientists released a pair of extensive studies on Saturday that point to a market in Wuhan, China, as the origin of the coronavirus pandemic. Analysing data from a variety of sources, they concluded that the coronavirus was very likely present in live mammals sold in the Huanan Seafood Wholesale Market in late 2019 and suggested that the virus twice spilled over into people working or shopping there. They said they found no support for an alternative theory that the coronavirus escaped from a laboratory in Wuhan (www.nytimes.com/interactive/2022/02/26/science/covid-virus-wuhan-originsl)

“When you look at all of the evidence together, it’s an extraordinarily clear picture that the pandemic started at the Huanan market,” said Michael Worobey, an evolutionary biologist at the University of Arizona and a co-author of both studies.

The two reports have not yet been published in a scientific journal that would require undergoing peer review.

Together, they represent a significant salvo in the debate over the beginnings of a pandemic that has killed nearly 6 million people globally and sickened more than 400 million. The question of whether the coronavirus outbreak began with a spill over from wildlife sold at the market, a leak from a Wuhan virology lab or some other way has given rise to pitched geopolitical battles and debates over how best to stop the next pandemic.

But some outside scientists who have been hesitant to endorse the market origin hypothesis said they remained unconvinced. Jesse Bloom, a virologist at the Fred Hutchinson Cancer Research Center, said in an interview that there remained a glaring absence of direct evidence that animals at the market had themselves been infected with the coronavirus.

In their new study, Dr. Worobey and his colleagues present evidence that wild mammals that might have harboured the coronavirus were being sold in December 2019. But no wildlife was left at the market by the time Chinese researchers arrived in early 2020 to collect genetic samples.

The authors of the new study include researchers who previously published smaller reports that had pointed toward a similar conclusion, but were based on much less detail. Their earlier analysis suggested that the first known case of the coronavirus was a vendor at the Huanan market.

In a separate line of research, scientists at the Chinese Center for Disease Control and Prevention carried out a new analysis of the genetic traces of coronaviruses collected at the market in January 2020. Previous studies have shown that the viruses sampled from early cases of Covid belonged to two main evolutionary branches. The Huanan market samples included both branches, the scientists reported in a study they posted online last weekend.

Dr. Worobey, who said he was not aware of the study until it was made public, said that their findings are consistent with the scenario he and his colleagues put forward for two origins at the market.

The Huanan Seafood Wholesale Market was an early object of suspicion when Covid first swept across Wuhan. Towards late December 2019, a few people who worked at the market developed a mysterious form of pneumonia. On Dec. 30, public health officials told hospitals to report any new cases of pneumonia linked to the market.

It also became clear at the end of December that a new coronavirus was to blame for the mysterious pneumonia. Coronaviruses have a disturbing history in China: In 2002, another coronavirus sparked the SARS epidemic, which killed 774 people. Scientists later concluded that the virus originated in bats, spread to wild mammals, and then jumped to humans at markets where the mammals were sold.

Fearing a replay of SARS, Chinese officials ordered the Huanan market closed. Wuhan police shut it down on Jan. 1, 2020. Workers clad in hazmat suits washed and disinfected the stalls.

Chinese scientists said they found the virus in dozens of samples taken from surfaces and sewers in the market, but not in any swabs taken from animals in the market.

The link to the market seemed to weaken as the coronavirus spread. Meanwhile, questions arose about the research carried out at a lab in the city, the Wuhan Institute of Virology, where scientists studied coronaviruses.

For the new studies, Dr. Worobey and his colleagues estimated the latitude and longitude of 156 cases of Covid in Wuhan in December 2019. The highest density of cases centred around the market.

The researchers then mapped cases in January and February. They used data collected by Chinese researchers from Weibo, a social media app that created a channel for people with Covid to seek help. The 737 cases drawn from Weibo were concentrated away from the market, in other parts of central Wuhan with high populations of elderly residents.

The patterns pointed to the market as the origin of the outbreak, the studies found, with the coronavirus then spreading to the surrounding neighbourhoods before moving out farther across the city. The researchers ran tests that showed it was extremely unlikely that such a pattern could be produced merely by chance.

“It’s very strong statistical evidence that this is no coincidence,” Dr. Worobey said.

The researchers also presented evidence that in late 2019, vendors at the market were selling raccoon dogs and other mammals known to be potential hosts of coronaviruses. Genetic samples collected from floors, walls and other surfaces at the Huanan market in January 2020 reveal traces of SARS-CoV-2 in the southwest corner of the market, where the vendors were clustered.

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At least 5.2 million children globally have lost a parent, grandparent or family caretaker to Covid-19, a new study says. The study, published on 24 February in The Lancet Child & Adolescent Health, said this “heart-breaking hidden pandemic” is nearing the total number of Covid-19 deaths, which currently stands at about 5.9 million people, according to latest World Health Organization totals. While plummeting Covid-19 case counts across the US are leading to a lifting of mask mandates, data shows more people are dying of Covid-19 now than during most points of the pandemic. More than 2,000 Covid-19 deaths have been reported in the US each day for the past month as the Omicron variant remains a heightened concern.

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The drive to help African countries produce vaccines with messenger RNA (mRNA) technology got big boosts last week from the World Health Organization (WHO) and the company BioNTech (www.science.org/content/article/news-glance-african-vaccine-n)

The success of mRNA COVID-19 vaccines made by the Pfizer-BioNTech collaboration and Moderna led to intense global demand, but African countries have had little access because of limited supply and high prices. Campaigns by several governments and nongovernmental organizations failed to convince the companies to freely share their technologies with economically strapped countries. So last year WHO launched a hub in South Africa to produce mRNA vaccines independently. The agency, which hopes the hub licenses a product by 2024, last week announced plans to train scientists from South Africa, Egypt, Kenya, Nigeria, Senegal, and Tunisia. BioNTech, which has been criticised for trying to undermine the WHO effort, separately announced that later this year it will train local scientists and send modular, shipping container–size vaccine factories to Ghana, Rwanda, and Senegal.

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In a setback to the global polio eradication campaign, a wild poliovirus has leapt from Pakistan to the African continent, where it has paralyzed a 3-year-old girl in Malawi(www.science.org/content/article/news-glance-african-n)

The case, announced on 17 February by the Malawi government, is the first wild polio case in the country since 1992. Pakistan and Afghanistan are the last two countries where the wild virus is endemic, which means circulation there has never stopped. Occasionally, however, the virus spills over from these entrenched reservoirs. Africa’s last known case of wild polio occurred in 2016 in Nigeria’s Borno state. The continent is still battling big outbreaks of vaccine-derived polio, however, which occur in areas of low immunization when the live but attenuated virus in the oral polio vaccine regains its ability to paralyse and spread.

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As people across the world grapple with the prospect of living with the coronavirus for the foreseeable future, one question looms large: How soon before they need yet another shot?

Not for many months, and perhaps not for years, according to a flurry of new studies (www.nytimes.com/2022/02/21/health/covid-vaccinel)

Three doses of a Covid vaccine — or even just two — are enough to protect most people from serious illness and death for a long time, the studies suggest.

“We’re starting to see now diminishing returns on the number of additional doses,” said John Wherry, director of the Institute for immunology at the University of Pennsylvania. Although people over 65 or at high risk of illness may benefit from a fourth vaccine dose, it may be unnecessary for most people, he added.

US Federal health officials have said they are not planning to recommend fourth doses anytime soon.

The Omicron variant can dodge antibodies produced after two doses of a Covid vaccine. But a third shot of the mRNA vaccines made by Pfizer-BioNTech or by Moderna prompts the body to make a much wider variety of antibodies, which would be difficult for any variant of the virus to evade, according to the most recent study, posted online last week.