简体中文
Scientists from various countries have found the existence of the novel coronavirus earlier than the first reported cases in China amid international efforts to piece together the puzzle of the COVID-19 origins.
At least nine recent studies have identified the virus in the U.S., Europe, Brazil and Japan, a sign that these pathogens emerged and circulated earlier than previously known.
U.S.: Virus found in blood samples in December 2019
A study published in June 2021 by the U.S. National Institutes of Health (NIH)
was the latest and largest (in scale) one to suggest that the new coronavirus popped up in the U.S. in December 2019, weeks before cases were first recognized by health officials.
Scientists at the NIH found antibodies to the novel coronavirus, known as SARS-CoV-2, in nine blood samples out of more than 24,000 people who gave blood between January 2 and March 18, 2020. Antibodies usually take about 14 days to develop.
Federal health officials are increasingly accepting a timeline in which small numbers of COVID-19 infections may have occurred in the U.S. before the world ever became aware of it.
"There was probably very rare and sporadic cases here earlier than we were aware of. But it was not widespread and didn't become widespread until late February," said Natalie Thornburg, principal investigator of the Centers for Disease Control and Prevention (CDC)'s respiratory virus immunology team.
Such results underscore the need for countries to work together and identify newly emerging viruses as quickly and collaboratively as possible, she added.
When did COVID-19 enter the U.S.?
A CDC-led study published in December 2020 that analyzed 7,000 blood samples suggested the virus infected some Americans as early as the middle of December 2019.
In the study published in the journal Clinical Infectious Diseases in November 2020
, CDC researchers tested blood samples from 7,389 routine blood donations collected by the American Red Cross from December 13, 2019 to January 17, 2020 for antibodies. The blood tests found SARS-CoV-2 antibodies in 106 of 7,389 blood donors.
France: Virus found in an ICU patient's sample collected in December 2019
First coronavirus case in France appeared in December: expert
Brazil: Virus found in sewage sample from November 2019
Exclusive: Brazilian researchers on discovery of COVID-19 virus in November sewage
Italy: Virus found in blood samples, sewage sample and skin sample
Study suggests traces of coronavirus in wastewater of Milan and Turin last December
A study by the National Cancer Institute (INT) of the Italian city of Milan published in November 2020 found blood samples taken in September 2019 showed the presence of antibodies against the SARS‑CoV‑2 virus.
"What we noticed, and it was unexpected, we found more than 10 percent of the samples presenting antibodies against the COVID-19 virus," INT biologist Gabriella Sozzi told CGTN. "This finding seems to tell us that the SARS‑CoV‑2 virus was probably circulating at a low level in Italy before the outbreak that we had in February."
The Italian researchers' findings,
published by the INT's scientific magazine Tumori Journal
, show that 111 out of 959 healthy volunteers enrolled in a lung cancer screening trial between September 2019 and March 2020 had developed coronavirus antibodies.
Study: Coronavirus emerged in Italy as early as Sept. 2019
Clues to COVID-19 origins include an anonymous skin sample in Italy from a 25-year-old Milan resident who in November 2019 visited a hospital with a sore throat and skin lesions. She left behind a skin sample that in two tests conducted more than six months later yielded traces of the virus, according to
research published in January by the British Journal of Dermatology.
Spain: Virus found in sewage samples
A study published in June 2020 by Spanish virologists at the University of Barcelona
discovered traces of the virus in samples of wastewaterfrom Barcelona collected in March 2019, 10 months before its first reported coronavirus case. The team had been testing sewage since April 2020 in order to identify new potential outbreaks of the virus.
Coronavirus traces found in March 2019 sewage sample: Spanish study
Japan: Virus found in blood samples
Two positive results were found in an investigation by
Japan's Ministry of Health, Labor and Welfare
among 500 blood donation samples collected from January to March in 2019 in Japan's Koshinetsu region.
The health ministry said there was a high probability that "false positives" occurred within a certain percentage of people who were not actually infected.
'False positive' of COVID-19 possible in 2019 blood samples in Japan
07:54
The studies with COVID-19-positive results are an example of the scattered clues about the pandemic's early days that could help determine how long the virus had been circulating the world before a cluster of cases erupted in central China's Wuhan in December 2019.
