The first confirmed coronavirus case in the U.S. was reported on Jan. 19 in a Washington man after returning from Wuhan, China, where the first outbreak of COVID-19 occurred.
Now, data from a new government study paints a different picture — the coronavirus may have been silently spreading in America as early as December 2019.
Researchers with the Centers for Disease Control and Prevention collected 7,389 blood samples from routine donations to the American Red Cross between Dec. 13, 2019 and Jan. 17, 2020.
Of the samples, 106 contained coronavirus antibodies, suggesting those individuals’ immune systems battled COVID-19 at some point.
A total of 39 donations carrying coronavirus antibodies came from residents in the western states of California, Oregon and Washington and 67 samples from the more eastern states of Connecticut, Iowa, Massachusetts, Michigan, Rhode Island and Wisconsin.
The study, published Monday in the journal Clinical Infectious Diseases, adds to growing evidence that the coronavirus had been spreading right under our noses long before testing could confirm it.
“The presence of these serum antibodies indicate that isolated SARS-CoV-2 infections may have occurred in the western portion of the United States earlier than previously recognized or that a small portion of the population may have pre-existing antibodies that bind SARS-CoV-2,” the study reads.
However, the researchers say “widespread community transmission was not likely until late February.”
Some of these early infections may have gone unnoticed because patients with mild or asymptomatic cases may not have sought medical care at the time, the researchers explain in the study. Sick patients with symptoms who did visit a doctor may not have had a respiratory sample collected, so appropriate testing may not have been conducted.
But the researchers wonder if the detection of antibodies in these patient samples really does indicate a past coronavirus infection, and not of another pathogen in the coronavirus family, such as the common cold.
A study published in August found that people who have had the common cold could have cells in their immune systems that might be able to recognize those of the novel coronavirus, McClatchy News reported.
Scientists behind the finding say this “memory” of viruses past could explain why some people are only slightly affected by COVID-19, while others get severely sick.
The researchers call this phenomenon “cross reactivity,” but they note it’s just one of several limitations to their study. The team also said they can’t tell if the COVID-19 cases were community- or travel-associated and that none of the antibody results can be considered “true positives.”
“A true positive would only be collected from an individual with a positive molecular diagnostic test,” the researchers wrote in the study.
Back in May, doctors in Paris also learned the coronavirus had been silently creeping around Europe a month before the official first-known cases were diagnosed in the region.
The first two cases — with known travel to China — in France were reported Jan. 24, but after testing frozen samples from earlier patient records, doctors realized a man with no recent travel had the coronavirus in December.