There are 11 times more undetected COVID-19 cases in the U.S. than reported ones and well over half a million people across the country could contract the disease in the next two months, new analysis has suggested.

The stark conclusions come from a research team at Columbia University which examined a New York Times database of known cases and linked it with Census Bureau data on commuting patterns and other data that were available through March 13.

The study found the virus was spread mostly by those who were unaware they are infected, or only displaying mild symptoms and that each infected person spreads it to an average of 2.2. other people. Even if the rate of transmission could be cut in half, which would require considerable effort and further societal lockdowns, as many as 650,000 people could become infected by May, it concluded.

“We’re looking at something that’s catastrophic on a level that we have not seen for an infectious disease since 1918,” Jeffrey Shaman, research team leader, told The New York Times. “It’s requiring sacrifices we haven’t seen since World War II. There are going to be enormous disruptions. There’s no easy way out.”

A woman cleans the Hollywod and Highland mall stairs in Hollywood on March 20, 2020, a day after Los Angeles County announced a near-lockdown, urging all residents to stay home except for essential needs. A study has suggested that more than half a million Americans might contract the disease in the next two months.

The research team’s model, which is only an estimate and does not include the states of Hawaii and Alaska, suggests that outbreaks in New York City, Seattle, Boston, and parts of California will spike, despite the tough restrictions already put in place to the movement of those populations.