Updated at 9:12 p.m. ET

President Trump doubled down Sunday on the suggestion that people facing the coronavirus should consider taking an anti-malaria drug that has not been proven to be an effective treatment.

British Prime Minister Boris Johnson, who was diagnosed with the coronavirus last month, has been admitted to the hospital for testing on the advice of his doctor, his office said Sunday.

"This is a precautionary step, as the Prime Minister continues to have persistent symptoms of coronavirus 10 days after testing positive for the virus," a spokesperson said in a statement.

Johnson announced on March 27 that he had tested positive. He said at the time that he had "mild symptoms" of COVID-19, including a fever and "a persistent cough."

The Pentagon was aware of the likelihood of a pandemic brought on by a novel coronavirus years ago, predicting with startling accuracy shortages of masks, hospital beds and ventilators that could occur in an outbreak, according to a 2017 internal document reported by The Nation.

New York Gov. Andrew Cuomo announced on Sunday that for the first time in days, the state has seen the daily number of deaths, hospitalizations and intubations as a result of COVID-19 decrease. More patients are also being discharged from hospitals.

"There's something a little bit different in the data today," Cuomo said, as state officials reported 594 new deaths on Sunday, down from 630 on Saturday.

St. Peter's Basicalla was virtually empty for Palm Sunday Mass, where usually tens of thousands would gather. Just a few nuns, prelates and laypeople gathered, abiding by social distancing guidelines, while Pope Francis livestreamed the mass in his homily.

Francis asked worshipers to think of others suffering from coronavirus.

An association representing thousands of hospitals across the country is pushing back after President Trump claimed that hospital administrators are "really thrilled to be where they are."

The American Hospital Association said hospital officials are worried about shortages of critical medical supplies, including medication for patients and personal protective equipment, or PPE, for health care workers.