A new study suggests that the coronavirus was infecting Americans as early as December 2019.

That would be weeks earlier than first believed and long before masks and social distancing became the norm.

Researchers, including those from the National Institutes of Health, looked at blood samples from 24,000 Americans, taken in the first three months of 2020. They found virus anti-bodies in enough samples to determine that the virus was popping up in mid-to-late December 2019, a finding that correlates with the latest findings by the Centers for Disease Control (CDC).

Initially, the CDC said the virus arrived in the US in mid-to-late January and early February of 2020.

A Washington state man was considered the first American to contract the virus after a visit to Wuhan, China, around Jan. 15.

About two weeks later, a Chicago woman, returning from Wuhan, was considered the first American to transmit the virus to another person -- her husband.

"There was probably very rare and sporadic cases earlier here than we were aware of," said Natalie Thornburg of the CDC. "But it was not widespread and didn't become widespread until late February."

There were plenty of Americans who reported getting sick with flu-like symptoms just before the virus exploded and later wondered whether if they had the virus or just the standard flu.

Notably, the NIH study found several participants in midwestern states who likely had the virus in December, far from the coasts of New York and Seattle, Washington where it took populations by storm in February.

The latest findings are not definitive and some experts are skeptical about the earlier timeline.

And while debate rages about how the virus originated in China, the CDC said tracing the specific timeline of its arrival is just as important.

Thornburg said the new findings underscore the need for countries to work together and identify newly emerging viruses as quickly and collaboratively as possible./aa