The study, published online by medRxiv and led by researchers at Icahn School of Medicine at Mount Sinai, traced the origin of the outbreak in New York City by analyzing complete genomes of the virus across four boroughs and two neighboring towns prior to March 18.
Researchers found that COVID-19 in New York City "predominately arose through untracked transmission between the United States and Europe, with limited evidence supporting direct introductions from China, where the virus originated, or other locations in Asia."
It is important to note that the study has not been peer reviewed.
With over 5,000 fatalities in the metropolitan area, New York City quickly became one of the major epicenters of SARS-CoV-2 -- more commonly known as COVID-19 -- infections in the U.S., according to the study.
Despite early initial screening measures and a series of nationwide travel restrictions from other infected nations like China, Iran and later Europe, the study identified the first case in New York on Feb. 29.
Research teams looked at 90 complete genomes of the virus from 84 of more than 800 confirmed positive COVID-19 cases within the Mount Sinai Health System.
"We sequenced complete genomes from COVID-19 cases identified up to March 18," Dr. Harm van Bakel, associate professor of genetics and genomic sciences at ISMMS, said. "These cases were drawn from 21 New York City neighborhoods across four boroughs (Manhattan, Bronx, Queens and Brooklyn), as well as two towns in neighboring Westchester County."
The team then analyzed these sequences together with all 2,363 publicly available SARS-CoV-2 genomes from around the world to determine the most likely origin of the SARS-CoV-2 strains infecting these metro New York City residents who sought care at Mount Sinai.
"Phylogenetic analysis of 84 distinct SARS-CoV2 genomes indicates multiple, independent but isolated introductions mainly from Europe and other parts of the United States," van Bakel said. "In addition, clusters of related viruses found in patients living in different neighborhoods of the city provide strong evidence of community transmission of SARS-CoV2 in the city prior to March 18, 2020."
"Only one of the 78 cases studied was infected with a virus that was a clear candidate for introduction from Asia, and that virus is most closely related to viral isolates from Seattle, Washington," Viviana Simon, a professor of microbiology and infectious diseases at ISMMS, said in a statement.
Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told ABC News' chief anchor George Stephanopoulos on Thursday that the new research is "probably correct" about how and when COVID-19 presented in New York.
"Europe became the epicenter pretty quickly after China really exploded with their cases. As you know, we cut off the travel from China relatively early and we were seeded with a relatively few number from China, but it quickly switched to Europe, particularly northern Italy," Fauci said.
"And given the travel and the air traffic from anywhere in Italy, particularly northern Italy, it's just not surprising -- unfortunately -- and inadvertently New York was seeded before they knew what was going on and that's why they're in the difficult situation they're in right now," Fauci explained.
What to know about coronavirus:
- How it started and how to protect yourself: Coronavirus explained
- What to do if you have symptoms: Coronavirus symptoms
- Tracking the spread in the US and Worldwide: Coronavirus map
The research team responsible for the study was made up of scientists and doctors the Icahn Institute for Data Science and Genomic Technology, the Global Health and Emerging Pathogens Institute, and the Departments of Microbiology, Pathology, and Genetics and Genomic Sciences.
This report was featured in the Friday, April 10, 2020, episode of "Start Here," ABC News' daily news podcast.
"Start Here" offers a straightforward look at the day's top stories in 20 minutes. Listen for free every weekday on Apple Podcasts, Google Podcasts, Spotify, the ABC News app or wherever you get your podcasts.