‘It affects virtually nobody,’ Trump says, minimizing the effect of the coronavirus on young people as U.S. death toll hits 200,000.

As he minimized the dangers the coronavirus poses to young people, President Trump falsely told supporters in Ohio on Monday night that the virus “affects virtually nobody,” hours before the country reached the grim milestone of 200,000 recorded deaths linked to the pandemic, according to a New York Times database.

Mr. Trump, who has veered back and forth between claiming that he takes the crisis seriously and dismissing it as a transient problem that will disappear on its own, made his remarks during a rambling late-night rally at an airport hangar in Dayton. They were part of a chain of assertions Mr. Trump made about the virus centered around the misleading claim, made by the president and other Republicans, that the virus only sickens the old and the ill.

“It affects elderly people, elderly people with heart problems, if they have other problems, that’s what it really affects, in some states thousands of people — nobody young — below the age of 18, like nobody — they have a strong immune system — who knows?” Mr. Trump said.

“It affects virtually nobody,” he added. “It’s an amazing thing — by the way, open your schools!”

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, has rejected that argument. He told CNN on Tuesday that 25 to 30 percent or more of the population has an underlying condition, like obesity, that contributes to their risk of severe illness.

“It can be serious in young people,” he said.

Mr. Trump’s comments, made in passing, were embedded in a long digression that began with a discussion of tax cuts and ended with his familiar exhortation for local officials to reopen their schools.

His mishandling of the virus, and his administration’s attempts to downplay or distort information about its severity, has emerged as a major vulnerability heading into the election, especially among educated suburban voters.

Mr. Trump continues to talk about the virus in dismissive terms, against the advice of advisers, who have urged him to talk less about the pandemic and more about the economy, law enforcement and other issues.

The true number of Americans killed by the virus — including thousands of people under 65 and some victims who seemed to be in good health before the illness struck — exceeds official death counts and is likely much higher than 200,000 already, according to a recent analysis of deaths in excess of normal levels compiled by The New York Times.

The University of Washington’s Institute for Health Metrics and Evaluation has estimated that as many as 378,000 Americans will have died in the pandemic by the end of the year if current trends continue.

The United States has recorded about 20 percent of the world’s fatalities even though the country is home to just 4 percent of the global population.