There's been a lot of debate in the scientific community — as well as among groups of friends where someone insists they had COVID-19 long before the first documented case was seen in Washington State — over when the coronavirus pandemic actually reached U.S. shores. Now there's another small study out of UCLA suggesting that Los Angeles may have seen its first cases before Christmas without anyone realizing it — at least a week before China even acknowledged the outbreak there.

The UCLA researchers worked with colleagues at the University of Washington to sort through medical records at all UCLA hospitals and clinics, and they made an interesting discovery. Whether you want to call it a coincidence with a bad flu strain circulating in late 2019, or you want to disbelieve the viral geneticists who have insisted that they can trace the age of the coronavirus strains that entered California based on mutations, the researchers say that there was a pattern they can't ignore in sick people in the LA area just before the holidays.

As the Los Angeles Times reports, the data at UCLA facilities shows an unmistakable bump in respiratory illnesses that began on December 22 and lasted into February. There was a 50-percent jump in the average number of patients reporting a cough during this three-month period compared to any of the previous five years — 1,047 more, for a total of 2,938. Some of these patients were treated at outpatient clinics, and some ended up admitted to Ronald Reagan UCLA Medical Center or other hospitals operated by UCLA.

That 2,938 number was also 34% higher than what was previously seen as the hospital systems worst winter for coughs, which was 2016-2017. The hospitals also had nearly 400 more patients than usual suffering from acute respiratory failure during that three-month period — and over 200 more than the previous worst winter for this condition, one year earlier.

None of these patients were tested for COVID-19 because diagnostic tests weren't being done here until mid-February and it was believed that the virus was mostly contained in China until then — though it would only be a week before the pandemic was spreading like wildfire in Italy and then throughout Europe. The outbreak of a mysterious and deadly pneumonia in Wuhan, China wasn't announced until December 31. The first U.S. case was believed to be in mid-January in Washington, though experts have suggested that that case was fully isolated and other infections were seeded in California at some later time. The first cases were documented in New York beginning in early March, and those have later been determined to have come into the country from Europe.

"It is possible that some of this excess represents early COVID-19 disease before clinical recognition and testing," writes Dr. Joann Elmore, a professor of health policy who co-authored the new paper.

The researchers believe that even if only a handful of these extra patients were indeed COVID-positive, they likely represent a tip of the iceberg of how widely the coronavirus was actually spreading undetected in the Los Angeles area.

A study released in May tended to suggest that the U.S. cases that seeded major outbreaks on the East and West coasts likely arrived later than was previously believed, rather than earlier. That study, done by researchers at UCSD, UCLA, the University of Edinborough and elsewhere, looked at viral genomes and epidemic models and concluded that, for example, that first Washington case was a dead end and had no connection to the broader outbreak in Washington weeks later. Also, it debunked the idea that a single outbreak in Germany in January was responsible for the cases that arose in Italy the following month.

But scientists have continued to say that none of these studies are likely to be the final word, and research will continue like the small-scale effort by the medical examiner in Santa Clara County in April that discovered a woman who had died at home of COVID complications in her heart in early February was actually the first documented U.S. death from the virus. Until then, the family had believed she had died from a sudden heart attack.

No doubt more studies in the coming months will reveal even more surprises like that one.

Related: New Study Rewrites the Timeline Of When COVID-19 Began Spreading In Washington State