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The introduction of the coronavirus through a laboratory incident is considered an "extremely unlikely pathway," for the origin of the virus, according to a report released Tuesday by the World Health Organization's joint international team.
Other more likely pathways to infection include transmission from an animal to a human or through the cold food chain, according to the team of 17 Chinese and 17 international scientists.
The team drew no firm conclusion about the role of the Huanan market in the origin of the outbreak, or how the infection was introduced into the market.
The coronaviruses most highly related to SARS-CoV-2 are found in bats and pangolins, suggesting that these mammals may be the reservoir of the virus that causes COVID-19, the report said. However, neither of the viruses identified so far from these mammalian species is sufficiently similar to SARS-CoV-2 to serve as its direct progenitor.
In addition, the high susceptibility of mink and cats to SARS-CoV2 suggests that additional species of animals may act as a potential reservoir.
The long-awaited report gives no definitive answer to the origin of the virus that has killed over 2.7 million people worldwide.
WHY THIS MATTERS
Tracking down the origin of COVID-19 may help prevent future outbreaks.
Over the weekend, former Centers for Disease Control and Prevention director Dr. Robert Redfield said he believed the virus was inadvertently leaked from a lab in Wuhan, China, where the virus was believed to have originated. It's not unusual for respiratory pathogens to infect lab workers, he said.
Redfield and infectious disease expert Dr. Anthony Fauci both have said they believe the virus was below the radar in October and November 2019 before it was first reported in December of that year.
THE STUDY'S LARGER TREND
The WHO team said it was unlikely that any substantial transmission of SARS-CoV-2 infection was occurring in Wuhan during October and November 2019.
The epidemiology working group identified earlier cases of COVID-19 through studies from surveillance of morbidity due to respiratory diseases in and around Wuhan in late 2019. It also drew on other data. In none of these studies was there evidence of an impact of the causative agent of COVID-19 on morbidity in the months before the outbreak of COVID-19, the report said.
The documented rapid increase in all-cause mortality and pneumonia-specific deaths in the third week of 2020 indicated that virus transmission was widespread among the population of Wuhan by the first week of 2020.
The steep increase in mortality that occurred one to two weeks later among the population in the Hubei Province outside Wuhan suggested that the epidemic in Wuhan preceded the spread in the rest of Hubei Province.
The team left open the possibility that positive cases of coronavirus were detected earlier than the first case in Wuhan, "suggesting the possibility of missed circulation in other countries," the report said. "So far, however, the quality of the studies is limited."
Also, SARS-CoV-2 has been found in frozen food, packaging and cold-chain products. The virus has been found on packages and products from other countries that supply China with cold-chain products, indicating that it could be carried long distances on cold-chain products, the team said.
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