White House trade adviser Peter Navarro warned in a late January memo the coronavirus could cost the United States trillions without a travel ban on China.

Navarro called for an immediate travel ban on China in the memo, dated January 29, that predicted a coronavirus pandemic would cost the United States over $3.8 trillion.

The details of the memo, which was first reported by the New York Times on Monday evening and later published in full by Axios, was addressed to the National Security Council just days before the president enacted his travel ban on China.

“The clear dominant strategy is an immediate travel ban on China,” Navarro wrote, noting the virus could cost as many as half a million American lives.

Navarro’s memo argued the financial cost of a travel ban with China would be minimal compared to the cost of doing nothing.

Donald Trump enacted his travel ban two days later, on January 31.

Navarro warned it was unlikely the virus would look like “seasonal flu,” at a time when many health experts were comparing coronavirus statistics to the numbers of Americans killed by the flu.

In a second memo dated February 23, Navarro warned of the need to acquire vast quantities of personal protective equipment for medical staff as they faced the virus.

Navarro warned the virus “could infect as many as 100 million Americans, with a loss of life of as many as 1-2 million souls.”

He also urged the White House to begin appropriating billions of dollars from Congress to prepare.

“Time is of the essence for all points of the PPE, treatment, vaccine, and diagnostics!” he concluded.