Two residents of Snohomish County, Washington, who fell ill with COVID-19-like symptoms in December have now tested positive for antibodies against the new coronavirus. The findings suggest the virus might have arrived in the U.S. earlier than thought.
One of these residents — identified only by her middle name Jean — says she fell ill shortly after Christmas with a dry cough, fever and body aches, according to The Seattle Times. Her illness eventually required two trips to the doctor along with chest X-rays and a prescription for an inhaled medication. At the time, COVID-19 had not been formally discovered or named as a disease entity. But this month, Jean received news from her doctor that a blood test showed she was positive for COVID-19 antibodies, The Seattle Times reported.
Nearly a month later, on Jan. 21, the first known case of COVID-19 in the U.S. would be reported in a Snohomish County man who had recently traveled to Wuhan, China.
Jean's test result isn't definitive proof that she had COVID-19 in December, because it doesn't show when she was infected. But local health officials who reviewed the results say that Jean is one of two people in the county found to test positive for coronavirus antibodies after falling ill with a COVID-19-like illness in December.
"They are being considered 'probable' [cases]," Heather Thomas, a Snohomish Health District spokeswoman, told The Seattle Times on Thursday (May 14).
However on Friday (May 15), Dr. Chris Spitters, the district's health officer, clarified that the word "probable" in this public health context doesn't mean the same thing as it would in everyday life. In this case, public health officials have to put cases into "certain buckets" to classify them, but those classifications may not match what they actually had, Spitters said in a COVID-19 briefing.
What's more, Spitters stressed that "the symptoms that those [two] individuals reported … overlap greatly with other respiratory tract infections," and it's possible they had something else. "There was no testing of those infections that occurred at the time, so it's possible and frankly, I think, more likely that they had a non-COVID respiratory viral illness in December and subsequently had an asymptomatic or minimally symptomatic COVID infection," he said. (In this scenario, it would be that later infection that wasn't obvious that imparted the person with COVID-19 antibodies.)
Still, experts say it's possible COVID-19 did come to the U.S. prior to the first reported case in mid-January. In France, doctors recently found genetic material from COVID-19 in samples taken from a patient treated in December, Live Science previously reported.
"The amount of air travel into and out of Wuhan was enormous, probably thousands and thousands of people," Dr. Art Reingold, a public health epidemiologist at the University of California at Berkeley, told The Seattle Times. "It follows that there [were] likely multiple introductions around the world, quite possibly in December." Rather than a single "patient zero," the disease was likely introduced into the country multiple times, he said.
Spitters acknowledged that, saying "I think it's reasonable to assume, given reports like the ones that we've had and others around the country, that introduction may have occurred prior to mid-January." However, "while that's of scientific and academic interest, it doesn't really change where we sit today or where we have to move ahead in the future."
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Originally published on Live Science.