Coronavirus spread undetected before testing showed public health problem, researchers say

Thousands of Americans in major cities such as New York and San Francisco were likely infected with the coronavirus well before testing showed that the disease’s outbreak posed a significant health problem in the U.S., according to estimates from Northeastern University researchers that were shared with The New York Times. 

The estimates are based on a model that tracked the spread of the disease in Boston, San Francisco, Chicago, Seattle and New York, which is considered the epicenter of the U.S. outbreak. The researchers found that infections were likely spreading in early February in multiple U.S. cities. 

While the U.S. had only confirmed 19 cases of COVID-19, the disease caused by the coronavirus, by March 1, the researchers’ model projects there may have been thousands of infections in those major cities alone.

About 28,000 people may have been infected with the disease by the first day of March, according to median estimates the model calculated for each city. The Times noted that the actual figure may have been substantially higher or lower. 

The U.S. has reported more than 840,000 confirmed coronavirus cases and more than 46,500 deaths caused by it, according to a Johns Hopkins University database.

Throughout the outbreak, the federal government has faced scrutiny over the availability of testing for the virus, with some governors noting that it’s been the number one problem they have faced. 

Alessandro Vespignani, the director of the Network Science Institute at Northeastern University and the woman who led the research, told The New York Times that amid the country’s early testing problems, a “silent chain of transmission” exposed thousands of people to COVID-19. 

The research team she led used a model that estimated for all infections, including people who have shown little to no symptoms. It also estimated for people whose exposure is never detected by testing.

Studies that research the spread of viruses typically predict how often people come into contact with one another as they work and socialize. The Northeastern model simulated movements based on where people fly, how they move and when they go to school, among other things, the Times noted.

The research from Northeastern arrived as officials continue to scrutinize how the virus rapidly spread in the U.S. It also came just a day after California officials said that autopsies on two people who died in early and mid-February showed they had been infected by the virus. 

Previously the first coronavirus death had been identified as a man in Washington state who died on Feb. 29.