Researchers tracking the spread of the coronavirus have determined that the virus has been circulating in New York City for a couple of months, since before testing began. Genetic sequencing of virus samples indicates most of the early cases in New York originated in Europe — not Asia — the researchers from NYU's Grossman School of Medicine found.

The research team studied samples of the virus taken from 91 New York City patients.

"As viruses evolve during transmission from person to person, their sequences can help researchers to zero in on the provenance, or place of origin, of that specific infection," Matija Snuderl, M.D., director of Molecular Pathology and Diagnostics at NYU Grossman, explained in a press release.

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The researchers have submitted the data to the Global Initiative on Sharing All Influenza as part of a worldwide effort to track the evolution of the novel coronavirus.

"This global effort does not just determine the code of a single version of the virus, but tracks how its genetic code changes as it moves through a population, and with what consequences," Snuderl said.

The standard coronavirus tests given to patients can only tell if a person is negative or positive for infection — not where the person caught the virus. The sequence information, however, can be used to figure that out, Dr. Matt Maurano, one of the researchers on the study, told CBS News.

"Obviously everything derives back to the December timeframe, to Hubei province in China," where the virus was first detected, he said. "But looking at more recent sources of infection, you can actually link clusters of cases. And I think there's an emerging consensus that if we were ever to move out of this lockdown stage, we're going to have to have a much better of idea of who is possibly transmitting the virus to the community."

Maurano said travel bans presumably had some effect on slowing infections from Asia, although bans happened in stages and initially didn't prevent the virus from coming in from places like Europe. President Trump's restrictions on travel from Europe didn't go into effect until mid-March, and by then the virus had already begun spreading more widely.

The data show that the virus had been spreading "fairly broadly for a period of time before we started sequencing," Maurano said.

Continuing this research will hopefully help guide how public officials respond to the pandemic.

"You can imagine in a couple of months, let's say the outbreak in New York has been suppressed, but there's an outbreak somewhere else," Maurano said. "What should we do? We can't really answer that question unless we have data on how the virus is spreading between regions or within the same region."

"The one way to think about this pandemic is that it's an information problem," Maurano said. "If we knew who had the disease and where they got it from, the rest of us could basically go back to work."

Another study out of New York City's Mount Sinai Icahn School of Medicine also found a majority of New York coronavirus cases originated in Europe, The New York Times reported.

Dr. Anthony Fauci, the nation's leading infectious disease expert and a member of the White House coronavirus task force, said these findings about the spread from Europe are "probably correct."

"Europe became the epicenter pretty quickly after China — really exploded with their cases," Fauci said on "Good Morning America" Thursday. "As you know, we cut off the travel from China relatively early and we were seeded with a relatively few number of cases from China. But very quickly the epicenter switched to Europe — particularly Northern Italy."

Fauci said that given the amount of air travel from Italy, it's not surprising that "unfortunately and inadvertently New York was seeded before they really knew what was going on. And that's why they're in the difficult situation that they're in right now."

Determining the sequences of the virus not only helps researchers monitor the spread and severity of the disease, it can also "clarify which drugs, vaccines, or social interventions are effective here," Adriana Heguy, PhD, director of the Genome Technology Center at NYU Langone Health, and leader of the sequencing team, said in the press release. "We're just starting this project, but will soon be sequencing 192 viral samples per week with the goal of offering thousands of sequences for analysis in the near future."