Outbreaks of the new coronavirus were already spreading undercover in major U.S. cities, well before testing showed a much larger issue, a new model developed by researchers at Boston-based Northeastern University estimates, according to The New York Times.
As of March 1, New York, San Francisco, Boston, Chicago and Seattle had collectively reported 23 confirmed cases of the virus. According to the new model, however, these cities had about 28,000 cases of the new coronavirus by that date.
In February, as the U.S. considered whether the outbreaks would grow and deem extreme social distancing and stay-at-home measures necessary, "in the background, you have this silent chain of transmission of thousands of people," Alessandro Vespignani, PhD, director of the Network Science Institute at Northeastern University and leader of the team that created the model, told the Times.
Other researchers said that the new model's estimates are "broadly in line with their own analyses," the Times reports.
There have been other indications that COVID-19 was spreading in the country earlier than previously thought. Autopsy results from Santa Clara County, Calif., show two patients with COVID-19 died in their homes on Feb. 6 and Feb. 17. Previously, officials had reported the nation's first COVID-19 deaths occurred when two people died of the disease in Seattle Feb. 26.