The claim: People who suffered from a round of illness in November and December likely had the coronavirus

A handful of widely circulated Facebook posts have asserted that people in the United States likely contracted the coronavirus as early as last fall.

“Who got sick in November or December and it lasted 10 to 14 days, with the worst cough that wouldn’t go away?” the posts say. “If you can answer, yes, then you probably had the coronavirus. There were no tests and the flu test would come back negative anyway. They called it a severe upper respiratory infection.”

Many of the posts currently circulating include the profile photo of a Facebook user named Donna Lee Collier. Collier did not respond to a USA TODAY request for comment on the origin of the posts.

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Bonnie Powell, of Waynesboro, Georgia, copied the status and received more than 230 shares. She said the post reflects her opinion, not necessarily scientific proof. But she said she had heard from friends about sickness at the end of last year, which makes her suspicious.

"Our area has had a very virulent 'flu' season with many of my friends testing negative for flu," she said in a Facebook message.

Coronavirus likely originated in November, was first in U.S. in January

Researchers have tied the origin of the virus to a live animal market in Wuhan, China. The World Health Organization first received a report of the outbreak on Dec. 31, but the virus originated in China more than a month earlier than that. A study published in early March by researchers at ETH Zurich puts the origin of the virus in the first half of November.

Fact check:Coronavirus originated in China, not elsewhere, researchers and studies say

Rumors surrounding the origins of the novel coronavirus have swirled as it spreads around the globe. Theories that the virus originated in a Chinese laboratory, or that it originated outside of China and was brought over by the U.S. Army, are not supported by evidence, according to medical experts. The virus is believed to have animal origins, likely in bats.

Fact check:Is COVID-19 caused by human consumption of animals?

On Jan. 21, the Centers for Disease Control and Prevention announced the first case of novel coronavirus in the United States from a person who had recently returned to Washington from Wuhan. The United States has since surpassed China and Italy to become the most infected country in the world, according to a tracker from Johns Hopkins University.

Symptoms of the novel coronavirus include a fever, cough and shortness of breath. Reported illnesses range from mild symptoms to severe symptoms and death.

Could the coronavirus have been in the U.S. before January?

Experts say it's plausible that coronavirus came over to the U.S. from China before that first January case, but more testing is needed to be sure.

"Anecdotally, we've heard about some influenza-like illnesses in December and January that were a little bit atypical," said Dr. Luis Ostrosky, a professor of infectious diseases at McGovern Medical School at UTHealth in Houston. "But the thing we need to solve that puzzle is when we actually start doing testing of antibodies, not just detecting the virus."

Ostrosky said that would include taking a look at blood samples from December and January to see if the virus was already in circulation.

Dr. Georges Benjamin, executive director of the American Public Health Association, said he believes when researchers do more testing, they will probably find the disease was in the U.S. earlier than first believed.

"I believe at the end of this, when we do look back – and we will – we will probably find that this disease was here earlier than we thought," he said. "We also know that when we closed our borders, it was very, very leaky."

However, Benjamin said it's "plausible but not likely" that the coronavirus was in the United States in November and December. If it were in the U.S. before the end of the year, the case would also have likely been connected to travel from China, he said, and likely not widespread.

Dr. Josh Petrie, assistant research professor at the University of Michigan School of Public Health, said it's important to remember that multiple existing viruses can cause severe upper respiratory symptoms and circulated late last year. Among them was Influenza B, which grew in intensity around November and December, as well as RSV and Influenza A.

He said it's possible there were "sporadic" travel-related cases earlier than the discovery of the first case but agreed it was likely not widespread as far back as November or December.

"There's a lot of surveillance that goes on for influenza every year, and so if we were seeing a lot of coronavirus activity at that time – even if you couldn't test for it – you would see signals in that influenza surveillance," he said.

Would already having the coronavirus make someone immune to further infection by it? That's also still under investigation. Ostrosky said that, in general terms, other coronaviruses do result in built-up immunity.

A New York Times article published Wednesday about research efforts underway to study antibodies characterized the answer to the immunity question as "a qualified yes, with some significant unknowns." Dr. Vineet D. Menachery, a virologist at the University of Texas Medical Branch at Galveston, told the Times that people who are infected may have one to two years of immunity, with any longer time span hard to predict.

Our ruling: More information needed

At this point, experts contacted by USA TODAY say it's unlikely that just because someone had a cough or other symptoms of an upper respiratory infection that they "probably had the coronavirus," especially as far back as November.

But it's also plausible that some cases did arrive in the U.S. earlier than the first reported case in January. Experts say additional testing and research is needed to get an exact picture.

Our fact-check sources:

Ian Richardson covers the Iowa Statehouse for the Register. Reach him at irichardson@registermedia.com, at 515-284-8254, or on Twitter at @DMRIanR.