Disagreement and uncertainty in the scientific community have been playing out in unusually public ways in these early months of the COVID-19 pandemic. And perhaps the most watched and most confusing debate has been about the timeline of when, where, and how quickly the coronavirus entered and spread in the United States.

Now, a new study has entered the fray and potentially overturns previous scientifically based assertions about this timeline — specifically the connection between the first documented case of COVID-19 in the Seattle area, and the outbreak that occurred in the region about six weeks later. Published on the site BioRxiv, the study by University of Arizona evolutionary biologist Michael Worobey and colleagues at UCSD, UCLA, the University of Edinborough, and elsewhere, suggests that the individual who had been called Patient Zero in the Washington outbreak did not, in fact, seed a series of community transmissions that ultimately found its way to a nursing home in Kirkland, Washington in late February. Through genetic sequencing and virus modeling, the study — which still needs peer review — found that it would have been impossible for the virus sample found in Patient Zero (also known as WA1) to have mutated into the virus that was found in the later Washington patients — and that virus strain had likely entered the state, possibly from China or from Vancouver, just two or three weeks before.

WA1, a Chinese national, flew into Sea-Tac Airport from Wuhan on January 14, and being aware of the coronavirus outbreak he sought medical treatment after showing symptoms and tested positive on January 19. Previously, geneticists had concluded that this man's virus sample was directly linked to one found in the nursing home patient known as WA2 six weeks later, on February 24. But the new study seeks to prove otherwise, and suggests that the "ebola-style lockdown" of WA1 in Seattle was indeed successful in containing the virus, contradicting earlier reports to the contrary.

Likewise, the study debunks a commonly held theory that an outbreak in Germany in late January that infected 16 workers at an auto supply company was the seed of the later outbreak in the Lombardy region of Italy. Data and models in this study similarly finds that the German outbreak was successfully contained through social distancing and extreme caution, and the virus made its way into Italy through other avenues. And it's been previously reported that the virus made it to New York City through at least a couple of channels via Europe.

As the New York Times explains, the new study lends credence to the argument that earlier social distancing measures in New York and elsewhere could have saved thousands of lives — and that banning air travel from China, as President Trump did on February 2, was not effective at preventing the spread of the virus in the U.S. It may, however, have slowed the spread of the virus to the West Coast, while much of the spread in the U.S. may ultimately be traced back to Italy or elsewhere in Europe.

Also, the study authors conclude that such work is vital to increasing the public understanding of what containment and mitigation efforts actually accomplish — for instance, in the first German outbreak, which was successfully contained.

Assertions that these efforts had actually failed may have led to confusion about the utility of these approaches and contributed to a sense of the inevitability of the spread of the pandemic. Similarly, conclusions that the Seattle area was already six weeks into an epidemic by the end of February, rather than two or three, and the notion that stringent efforts to prevent spread had failed in the WA1 case, may have influenced decision-making about how to respond to the outbreak, including whether such measures were worth the effort.

The latest study findings will further frustrate arguments by those in California who believe the virus was spreading here as early as December. Most scientists who have been studying the slow mutation of the coronavirus have concluded that is not possible, though the debates about this are likely to rage on — and more evidence is likely to emerge on either side.

Other studies will need to look at how the virus made it to California in late January and early February. We recently learned that 57-year-old Patricia Dowd of San Jose died of apparently COVID-related heart failure on February 6, marking perhaps the first U.S. death from the virus — and suggesting California may have been on its own timeline of transmission, separate from Washington state. Previously, the nursing home patient in Kirkland, Washington who died on February 29 was thought to be the first U.S. casualty of the virus.

Last month, a computer model made by researchers at Northeastern University suggested that San Francisco could have had as many as 9,000 undetected COVID-19 cases by March 1, though that now seems implausible.

Dr. George Rutherford, an infectious disease expert at UCSF, spoke to the Chronicle in April and suggested that the early cases in Santa Clara were likely all linked directly to travelers from China — and that the virus likely made several failed entry points into the region before it ultimately took off on a successful path of community transmission.

Dr. Charles Chiu, director of the UCSF-Abbott Viral Diagnostics and Discovery Center, similarly said, "Based on sequencing, we can tell [the virus] came into the country sometime in February when all of this began. What probably happened is that there was either one or multiple introductions in Santa Clara County, but there is no evidence that it had been circulating widely prior to that time."

To recap: In conjunction with some previous other work, it would seem the coronavirus made its entrances into California and Washington around the same time, in early to mid-February, and into New York perhaps slightly later, though more virulently, via Europe. And another study by a group of computational biologists asserted that the strain of the virus that arrived from Europe is more easily transmissible and has become the more dominant strain in every region where it has arrived.

Related: Researchers Find Now Dominant Strain of Coronavirus Is More Contagious, Came From Europe Mutation