Research Sheds New Light On Coronavirus Origins, Early Wuhan Cases

New research by US-based Canadian scientist Michael Worobey sheds further light on the role of the Wuhan market in the human origins of SARS-CoV-2.

Source: Brian Yang/Scrip

WUHAN'S HUANAN MARKET IN JUNE 2020

Days before the first clusters of human coronavirus infections were identified in December 2019, sporadic cases had surfaced in areas surrounding the Huanan wet market in the Chinese city of Wuhan, a new report finds. Some of these cases had no known connections to the market while others had indirect confirmed links.

An overview of the initial outbreak shows the early onset of infections with the novel SARS-CoV-2 virus might have been due to person-to-person transmission for some time before the first cluster was identified. Despite their sporadic nature and the indirect links to the huge Huanan live animal market in the city's Jianghan district, "there was a genuine preponderance of early COVID-19 cases associated with Huanan Market," notes Dr Michael Worobey, scientist at the University of Arizona, in a newly published analysis in Science, “Dissecting the early COVID-19 cases in Wuhan.”

The author, who was among the scientists who wrote an open letter in May around the origin of the virus and the possibility of a research laboratory leak in Wuhan, combed through local hospital and other reports and noted that “forty-one of the first known patients formed the basis of an influential study that reported that 66% — i.e., not all early cases — had a link to Huanan Market.”

The fact that "most early symptomatic cases were linked to the Huanan Market - specifically the western section where racoon dogs were caged [and sold] - provides strong evidence of a live-animal market origin of the pandemic," Worobey concludes. 

However, when the virus actually jumped from a wild animal, widely believed to be the racoon dogs, and when human transmission of the virus started, remain unsolved. The Huanan Market was shut down and disinfected on 1 January 2020, when testing conducted by Chinese labs on over 100 animals all turned out to be negative. 

 

Nevertheless, the fact so many of the more than 100 COVID-19 cases from that December, even those with no identified link with the market, lived in its direct vicinity "provides compelling evidence that community transmission started at the market," Worobey writes. 

First Cases, Cluster

The Science report looks at specific individual cases, including one of the earliest of those reported, a female seafood vendor who developed symptoms on 11 December 2019. Another, a male accountant who lived 30km away from the market, had a medical emergency on 8 December but didn’t show symptoms such as fever until the 16th of that month. 

Meanwhile, another couple sought medical care at Hubei Provincial Hospital of Integrated Chinese and Western Medicine (HPHICWM), where the director of virology and emergency medicine took a CT scan image revealing what looked like “ground glass” in their lungs. Their son, who was asymptomatic, underwent a scan and similar lesions were discovered. The individuals were not directly linked to the market but formed part of the first cluster of coronavirus infections documented by the World Health Organization.

China’s virus pneumonia of unknown etiology (VPUE) mechanism, established after the SARS outbreak in 2003, did not report any of the early cases until much later and these were reported according to clinical presentation, not epidemiologic information, Worobey notes.

 

The virus circulated in Wuhan for most of December 2019 and on the 29th of that month, a physician at the HPHICWM alerted the Wuhan Commission of Health and Center for Disease Control; the municipal health authorities issued an emergency alert the following day.

Although the WHO sent a delegation to investigate the true origin of the virus and issued a report, some scientists have continued calling for a thorough investigation through genomic analysis of the early cases, and additional epidemiologic data, notes the author.

Conclusive evidence of a point of origin from wildlife at the Huanan Market may be obtainable through analysis of spatial patterns of early cases and from additional genomic data, including SARS-CoV-2-positive samples from the market, as well as through integration of additional epidemiologic data, Worobey concludes.

“Preventing future pandemics depends on this effort.”

Slow Booster Roll-Out

Meanwhile, on 15 November, China's National Health Commission issued a fact sheet concerning the roll-out of booster coronavirus vaccines to people over 18 years old in the country. The shots are available to anyone who has been fully vaccinated for over six months and those who received a single-shot adenovirus-based vaccine. 

The available boosters are all from domestic manufacturers - two from Sinopharm Group Co. Ltd., one from Sinovac Biotech Ltd. and the other, an adenovirus-based vaccine, is from CanSino Biologics Inc.

The booster effort has not received as much enthusiasm in China as the initial COVID-19 jabs, which many believed were necessary given the Chinese government’s "zero COVID" policy and continued closed borders for travel. Furthermore, China has yet to make more effective mRNA vaccines available to the public and there are no real-world data showing actual protection and efficacy rates and the waning over time of the efficacy of the country's domestically developed inactivated vaccines.

Without such information and no better alternatives, many have chosen to wait and see instead of getting the booster shot. As of 19 November, official data show that 1.76 billion people had been fully vaccinated in China, putting the vaccination rate at 76.9% of the population, one of the highest proportions globally for a major country.