When did the coronavirus arrive in the United States?
The first infection was confirmed on January 21, 2020 in a resident of Washington state who recently returned from Wuhan, China. Shortly afterwards, experts concluded that the virus had been in the country for weeks.
A study published Tuesday provides new evidence: based on an analysis of blood tests, scientists have identified seven people in five states who may have been well-infected before the first confirmed cases in those states. The results suggest that the virus, for example, spread to Illinois as early as December 24, 2019, although the first case in the condition was confirmed a month later.
Some experts said the new study is flawed: the possibility that the antibodies against coronaviruses that cause colds are not adequately treated, and the results could be a stimulus to the tests used. In addition, the researchers also did not have travel information for any of the patients, which could help explain the test results.
“This is an interesting article because it raises the idea that everyone thinks it’s true, that there were infections that were not diagnosed,” said Scott Hensley, an immunologist at the University of Pennsylvania.
But the small number of samples tested positive makes it difficult to be sure that these are true cases of infection and not just a methodological error. “It’s hard to know what is a true signal and what is not,” he said.
However, if the findings are accurate, it underscores the idea that poor testing in the United States missed most cases during the early weeks of the pandemic.
“Without testing, you can not see what’s going on,” said Keri Althoff, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health and lead author of the study. “In these earlier months in some of these countries where we did not suspect, there was a lot of contagion going on.”
It is not surprising that there were undocumented cases early in the pandemic, said Sarah Cobey, an evolutionary biologist at the University of Chicago. Experts ‘already knew this was the case from studying trends in excessive deaths and hospitalizations,’ she said.
Dr. Cobey’s latest model estimates that there were approximately 1,000 infections in Illinois on March 1, 2020. “Given the terrible condition of the testing, there was never any doubt that we were missing the earliest transfer,” she added.
In the study, published in the journal Clinical Infectious Diseases, dr. Althoff and her colleagues analyzed blood samples from more than 24,000 people. They found nine people who donated blood between January 2 and March 18 last year, who apparently had antibodies against the coronavirus.
15 June 2021, 15:29 ET
Seven of the samples came from blood donated before the date of first diagnosis in their states – Illinois, Wisconsin, Pennsylvania, Mississippi and Massachusetts. The results are similar to those of another study identified coronavirus antibodies blood already donated in mid-December 2019.
The participants are enrolled in a long-term project of the National Institutes of Health, called We all, which aims to include a million people in the United States, thereby increasing the representation of minorities in research. Only half of the people in the study were white.
Early in the pandemic, the virus would have infected very few people. A low incidence increases the chance that an antibody test will incorrectly identify a sample as antibodies if it is not, said Dr. Hensley said – a false positive reaction.
The researchers tried to reduce the possibility by using two antibody tests in sequence. The first test indicated 147 samples as possible antibodies against the coronavirus; the second decreased the number to nine.
The team also analyzed 1,000 blood samples from the cold and flu season 2018-19 and found that no one tested positive for antibodies against the coronavirus.
“It is still quite possible that some of them may be false positives,” said Dr. Josh Denny, CEO of All of Us, said. But “the fact that everyone is false positives seems pretty unlikely with what we did.”
The researchers said they intended to contact participants to inquire about the travel history and will continue to analyze additional samples to estimate when the coronavirus will reach U.S. shores.
“The exact month in which it probably arrived in the US is still unknown,” said Dr. Althoff said. “It’s actually a puzzle, and our study is just one piece of the puzzle.”