Bill Gates said the US should shutdown the entire country for a short period of time to prevent the spread of the coronavirus.
He also predicted that the number of cases will peak in late April warned that ending shutdowns early could be disastrous.
In an interview with CNN Gates said, "It is exponential growth if you are not stopping it. The sooner you engage in the shutdown, the easier it is to get to that peak. We have not peaked."
"Never in my lifetime have we had to change our behavior and have this drastic effect on the economy in order to save lives," Gates said.
Gates pushed for more shutdowns and shelter-in-place orders, even in states with relatively small numbers of confirmed cases. The billionaire philanthropist said infected travelers from states that didn't aggressively shut down could reignite outbreaks in states that did.
"The whole country has to be in this together," he said.
Cases continue to skyrocket and health care systems in cities like New York are being overwhelmed by patients.
The Microsoft co-founder said that could have been avoided had the US prepared a response months ago and aggressively tested for new coronavirus cases, isolating and tracing contacts of the infected.
Gates said a lack of testing made that outcome impossible.
"We're quite blind to a lot of these cases right now," Gates said. "The light is not at the end of the tunnel in terms of a mid-April reopening."
Gates also indirectly pushed back at President Donald Trump, who has repeatedly said he wants the shutdown orders lifted in two weeks to lessen the economic impact. Gates called that timeline "not realistic."
"The numbers are still going up," he said. Shutdowns should only be lifted once cases drop significantly, he added.
Progress toward the treatment of the disease is being made, Gates said. A "therapeutics accelerator" at the Bill and Melinda Gates Foundation is looking at "promising compounds" that could be used to treat the coronavirus, but a potential vaccine is still months away.
In the meantime, a "middle course" option of a temporary shutdown isn't feasible, Gates warned.
He said, "The sooner we take this medicine, which is tough medicine, the sooner we'll be out of it and not have to go back into it again."