Report on COVID origins highlights clues to animal-human jump

SARS-CoV-2 under microscope
SARS-CoV-2 under microscope

Rawpixel Ltd / Flickr cc

The international team that traveled to Wuhan, China, to investigate the source of SARS-CoV-2 published its full findings today, which cover four possibilities, but the experts say a jump to humans from an intermediate animal carrier is the likeliest scenario based on promising clues.

The World Health Organization (WHO)-led team published its 120-page report on the WHO's website and fielded questions today. Release of the findings, however, prompted high-level calls for more transparency from China, including from the WHO's director-general.

In other developments, global leaders and organizations today called for an international "pandemic treaty" focusing on pandemic preparedness and response efforts to build a more robust global health system to protect future generations.

First step in exploring source

The 10-person joint mission team traveled to China in January, spending nearly 4 weeks on the investigation. The group's work was prompted by a May 2020 resolution by the World Health Assembly, which asked the WHO to identify the zoonotic source of the virus and how it passed to humans.

The source of the virus has been a flashpoint, playing out against the backdrop of political tensions between western nations and China. Some groups have questioned China's transparency about the source of the outbreak, which led to speculation that the virus may have come from a lab.

At today's briefing, Peter Ben Embarek, PhD, who led the WHO team, said the team identified four potential pathways, including a direct introduction from animals, a jump from an intermediate host, frozen food contamination, and an lab accident or leak. He said the team stuck to the hard facts about each possibility, while weighing the likelihood of each of them. WHO officials today emphasized that all possibilities remain under consideration and that the investigation is the first step in exploring the source of the virus.

Thea Fisher, MD, PhD, from Nordsjaellands Hospital in Denmark, who was involved in the epidemiologic assessment, said the team looked at thousands of data points, including early cases that may signal unidentified earlier outbreaks. So far, no evidence of early substantial outbreaks has been found, and she said researchers will revisit the possibility when serology studies are conducted to look for any traces of the virus in the months preceding the outbreak.

Marion Koopmans, DVM, PhD, from Erasmus Medical Center in the Netherlands, said a key conclusion was that the Wuhan market at the center of the early outbreak was an important amplifying event, with some genetic diversity already seen in the virus samples, hinting at some missed transmission chains that will require deeper digging.

Peter Daszak, PhD, with EcoHealth Alliance in the United States, said investigators found clear links and pathways that could have taken wildlife to the market from places where the closest relatives of SARS-CoV-2 are found, which brings investigators closer to a final answer.

Ben Embarek said of the group's report, "It's clear that there is still a lot of work to do. There are good leads in the recommendations." He urged people to view the report as a dynamic product, with findings that will be evaluated based on new information.

He said it's natural to consider the lab-release possibility, because facilities are located near the outbreak areas. However, Ben Embarek said for now, there is no evidence of a lab link. He added there are other, more concrete and interesting leads that focus attention on the intermediary animal source possibility.

Dominic Dwyer, MD, from Westmead Hospital in Australia, said a true forensic investigation of the lab was outside the scope of the WHO's investigation.

The experts acknowledged they were operating in a political environment but were never pressured to remove critical elements from the report. "We were able to create a space for science," Ben Embarek said.

Concerns about delays, incomplete access

In remarks to WHO member states today, WHO Director-General Tedros Adhanom Ghebreyesus, PhD, thanked the research team for their hard work under high-pressure conditions and for detailing their findings.

The report advances the understanding of the source of the virus, but raises more questions, such as how early the virus was circulating. He said the team has voiced problems accessing raw data and biological samples from earlier months. "I expect future collaborative studies to include more timely and comprehensive data sharing," Tedros said.

He also noted that the role of animal markets is still unclear, with more research needed that includes farmers, suppliers, and their contacts.

Tedros also said he didn't think the lab assessment was extensive enough. Although the team has concluded that a laboratory leak is the least likely hypothesis, this requires further investigation, potentially with additional missions involving specialist experts, which he is ready to deploy.

In a related development, a joint statement from the United States, Australia, Canada, United Kingdom, and 10 other nations said they support the investigations but have concerns about the delay in the investigation and that the group lacked access to complete, original data and samples.

"We share these concerns not only for the benefit of learning all we can about the origins of this pandemic, but also to lay a pathway to a timely, transparent, evidence-based process for the next phase of this study as well as for the next health crises," the group wrote.

Urgent call for 'pandemic treaty'

In another key development today, heads from 25 governments and international groups, including the WHO, issued an urgent call for an international pandemic treaty for pandemic preparedness and response. The effort seeks to build a more robust global health system that would protect future generations.

Leaders made their case for the treaty in a commentary published in several newspapers. "There will be other pandemics and other major health emergencies. No single government or multilateral agency can address this threat alone," the group wrote.

The United States and China were not among the countries signing on to the call, though there were some from other major economies, especially in Europe.

In other global headlines:

  • As cases rise in several European locations, Turkey announced it is tightening its measures; in Austria, an Easter lockdown has been ordered for Vienna; Spain is now experiencing a gradual increase in cases; and a Russian official said the country is experience a third surge in cases.

  • A poll of 77 epidemiologists from 28 countries by the People's Vaccine Alliance warned today that coronavirus variants may soon threaten the effectiveness of currently authorized COVID-19 vaccines, per a press release from Oxfam International. Two thirds of respondents predicted that variants will be able to evade the vaccines within a year, while nearly a third shortened that timeframe to no more than 9 months. Eighty-eight percent said that vaccine shortages in many countries will increase the odds of the emergence of new vaccine-resistant strains.

  • A technical report from the European Centre for Disease Prevention and Control (ECDC) said reinfections with COVID-19 are very rare, and early indications suggest that onward transmission is reduced in those who are vaccinated.

  • Germany today became the latest country to recommend that the AstraZeneca-Oxford vaccine be restricted in people younger than 60 while health officials investigate possible links to blood clots. The country's regulators are examining 31 blood clot cases with suspected vaccine links.

  • The global total today approached 128 million cases, rising to 127,987,404 with 2,797,124 deaths, according to the Johns Hopkins online dashboard.

This week's top reads