A new analysis of blood samples from 24,000 Americans taken early last year is the latest and largest study to suggest the novel coronavirus may have emerged in the United States in December 2019 — weeks before cases were first identified by health officials.
The analysis is not definitive, and some experts remain skeptical, but federal health officials are increasingly accepting of a timeline in which small numbers of COVID-19 infections may have occurred in the United States before the world became aware of a dangerous new virus emerging in China. .
“The studies are largely consistent,” said Natalie Thornberg, principal investigator on the U.S. Centers for Disease Control and Prevention’s Virus Immunology Team.
“There may have been very rare and sporadic cases here earlier than we were aware of. But it was not widespread and did not spread until late February.”
The pandemic coronavirus emerged in Wuhan, China, in late 2019. Officially, the first identified US infection was a traveler – a Washington state man who returned from Wuhan on January 15 and sought help at a clinic on January 19.
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CDC officials initially said that the spark that started the outbreak in the United States arrived during a three-week window from mid-January to early February. But research since then — including some by the CDC — has suggested a small number of infections occurred earlier.
A study led by the Centers for Disease Control and Prevention (CDC) published in December 2020, which analyzed 7,000 samples of American Red Cross blood donations, indicated that the virus infected some Americans as early as mid-December 2019.
While it is entirely plausible that the virus was introduced to the United States much earlier than would normally be expected, that does not mean that this is necessarily strong enough evidence to change the way we think about this.– William Hanage, expert in disease dynamics
latest study, Published online Tuesday in the journal Clinical Infectious Diseases, by a team that includes researchers at the National Institutes of Health (NIH). They analyzed blood samples from more than 24,000 people across the country, collected in the first three months of 2020 as part of a long-term study called “All Of Us” that seeks to track one million Americans over years to study health.
Like the CDC study, these researchers looked for antibodies in the blood that are taken as evidence of coronavirus infection, and can be detected as early as two weeks after a person is first infected.
Possible previous cases mentioned in 5 states
Researchers say nine study participants — five from Illinois and one each from Massachusetts, Mississippi, Pennsylvania and Wisconsin — were infected before any COVID-19 case was reported in those states.
One of the Illinois cases became infected on Christmas Eve, said Keri Altoff, an assistant professor at the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland, and lead author of the study.
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It can be difficult to distinguish between antibodies that neutralize SARS-CoV-2, the virus that causes COVID-19, and antibodies that fight other coronaviruses, including those that cause the common cold. Researchers in the NIH and CDC studies used multiple types of tests to reduce false positives, but some experts say their 2019 positive results could still be infection with other coronaviruses rather than the pandemic strain.
William Hanage, of Harvard University, said: “While it is entirely plausible that the virus was introduced to the United States much earlier than is usually estimated, this does not mean that this is necessarily strong enough evidence to change the way we think about this. “. University expert in disease dynamics.
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NIH researchers have not yet followed up with study participants to see if any of them had traveled outside the United States prior to infection. But they found it worth noting that the nine were not living in or near New York City or Seattle, where the first wave of cases was concentrated in the United States.
“The question is how and where the virus took the seeds,” Altov said.
The new study, she said, indicates that it “is likely that its seeds are located in multiple places in our country.”