Chart of the day: Discovery of coronavirus cases earlier than Wuhan outbreak
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
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.
Brazil: Virus found in sewage sample from November 2019
A Brazilian research team found samples of the novel coronavirus in the sewer system of the southern city of Florianopolis back in late November 2019, three months before the first coronavirus case was officially recorded in the country on February 26, 2020.
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."
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.
"These results, sent to a high impact journal and published in the archive medRxiv, suggest the infection was present before knowing about any case of COVID-19 in any part of the world," the statement said. "Those infected could have been diagnosed with flu in primary care by mistake, contributing to the community transmission before the public health authorities took measures."
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.