WASHINGTON - The US government's top infectious disease expert has told a House committee the next few weeks will be critical to arresting the country's disturbing coronavirus resurgence.
Dr Anthony Fauci issued a plea before Congress on Tuesday for people to avoid crowds and wear masks – just hours before mask-shunning President Donald Trump was set to address a crowd of his young supporters in one hot spot, Arizona.
Dr Fauci and other leading health officials also said they had not been asked to slow down virus testing, in contrast to Mr Trump's claim last weekend that he had ordered fewer tests be performed because they were uncovering too many infections.
Mr Trump said earlier on Tuesday he was not joking when he made that remark, despite comments to the contrary from the White House.
"We will be doing more testing," Dr Fauci, infectious disease chief at the National Institutes of Health, told a House committee conducting oversight of the Trump administration's response to the pandemic.
Dr Fauci told politicians he understood the pent-up desire to return to normal as the US begins emerging from months of stay-at-home orders and business shutdowns.
But he said that had to be "a gradual step-by-step process and not throwing caution to the wind".
"Plan A, don't go in a crowd. Plan B, if you do, make sure you wear a mask," Dr Fauci said.
Troubling surges worsened on Tuesday in several states, with Arizona, California, Mississippi, Nevada and Texas setting single-day records for new coronavirus cases. Some governors said they would consider reinstating restrictions or delaying plans to ease them in order to help slow the spread of the virus.
Arizona, where Mr Trump gave a speech at a Phoenix megachurch, reported a new daily record of nearly 3,600 additional coronavirus infections on Tuesday.
Arizona emerged as a Covid-19 hot spot after Republican governor Doug Ducey lifted his stay-home orders in mid-May. Last week he allowed cities and counties to require masks in public places and many have done so.
Texas surpassed 5,000 new cases for a single day for the first time — just days after it eclipsed 4,000 new cases for the first time — as America's largest paediatric hospital began taking adult patients to free up bed space in Houston. The infection rate in Texas has doubled since late May.
And Nevada surpassed a record one-day increase for the fourth time in the past eight days.
Other states also were experiencing worrisome surges, including Louisiana, Utah and South Carolina.
Another concerning trend is an increase in infections among young adults.
Dr Fauci said while Covid-19 tended to be less severe in younger people, some of them did grow very sick and even died. Younger people also may be more likely to show no symptoms yet still spread the virus, he said.
Some 2.3 million Americans have been infected and some 120,000 have died, according to data from Johns Hopkins University.
Mr Trump, meanwhile, doubled down on testing claims that have public health experts appalled, tweeting on Tuesday: "Cases are going up in the U.S. because we are testing far more than any other country, and ever expanding. With smaller testing we would show fewer cases!"
Less testing in fact means more infections going undetected.
The US was slow in ramping up testing and is currently testing some 500,000 people a day. Many experts say to control the spread of the virus, it should be testing 900,000 or more.
As for the anxiously awaited vaccine, Fauci said he believes "it will be when and not if" it arrives, and he is "cautiously optimistic" that some vaccine could be available at the end of the year.
About 2.3 million Americans have been infected and over 120,000 have died.