President Trump dismissed the severity of the coronavirus pandemic in the United States over the weekend, downplaying the impact of the disease and saying that while the testing of tens of millions of American had identified many cases, “99 percent” of them were “totally harmless.”

His remarks about a virus that has already claimed nearly 130,000 lives were perplexing. The coronavirus is surging across the Sunbelt states and has rebounded in California. At least 2.8 million Americans are known to be infected, and public health officials have said the real number of infections may be 10 times higher.

WHAT WAS SAID

Likewise, testing — there were no tests for a new virus, but now we have tested over 40 million people. But by so doing, we show cases, 99 percent of which are totally harmless. Results that no other country will show, because no other country has testing that we have — not in terms of the numbers or in terms of the quality.

False. No matter how you define harmless, most public health experts and respected coronavirus disease models would flatly contradict Mr. Trump’s assessment.

Calculating the toll of a rapidly moving pandemic while it is still raging is a Sisyphean feat, with outbreaks popping up in different parts of the country, even as improvements in care and new therapies curb mortality rates.

Experts say the president appears to have seized only on a death rate estimate of 1 percent or less that does not capture the entire impact of the disease, and excludes a multitude of thousands who have spent weeks in the hospital or weeks at home with mild to moderate symptoms that still caused debilitating health problems.

That death rate is narrowly focused on the number of people who die as a percentage of the total number of people affected — including those who are asymptomatic and do not experience any illness, and those with mild cases, who experience fleeting symptoms.

A crude calculation of the U.S. death rate, based on the total number of deaths officially attributed to the virus and the number of cases diagnosed through testing, suggests the mortality rate is higher, with 4.5 percent of those infected dying. But many experts agree that this rate is very likely inflated, because the denominator at this point in time has missed so many cases, including those who were never diagnosed because of testing shortages as well as those who were asymptomatic.

And some experts pointed out that even those who tested positive but show no symptoms should not be considered cases that are harmless — they can unwittingly transmit the virus to others in the community who are more vulnerable and may develop an acute illness.

Studies that have calculated the death rate based on broader antibody testing that takes these silent cases into consideration suggest an infection death rate of less than 1 percent, said Dr. Ashish K. Jha, the faculty director of the Harvard Global Health Institute.

“It’s always tricky to do this in the midst of a pandemic,” Dr. Jha said. “There are a lot of factors that go into it. But let’s say you took 1,000 Americans at random who were all infected. Our best guess is that between six and 10 would likely die of the virus.”

And the death rate does not capture all of the harm caused by the disease. As many as 15 to 20 percent of known Covid-19 patients may require hospitalization, and of the group admitted, 15 to 20 percent are transferred into intensive care, according to some estimates.

In addition to hospitalization, another consideration that would complicate what defines harmlessness is the long-term implication for so many who have recovered or are still struggling to regain their pre-Covid lives.

Patients fortunate enough to survive a lengthy hospitalization and weeks in an intensive care unit or on a ventilator face a long road to recovery. Many will suffer debilitating long-term effects, including impaired lung function, neurological problems and cognitive deficits, and some may require lifelong care and not regain full independence.

Some patients have prolonged courses of illness, with fevers and weakness that lasts for weeks on end; the disease has also been linked to strokes that can be disabling, and much about how the disease affects the immune system long term is still unknown. Residual symptoms such as continuing shortness of breath, muscle weakness, flashbacks and mental fogginess can persist for some time.

“We don’t fully appreciate the long-term consequences of having Covid, even mild and moderate forms of Covid that were never admitted to the hospital,” said Dr. Thomas McGinn, the deputy physician in chief at Northwell Health and director of the Feinstein Institutes for Medical Research, who is studying the disease’s long-term effects.

“Are there lingering effects lasting three months, six months, a year or longer? The question of what percent have long-term consequences, and the severity of the consequences, are unclear,” Dr. McGinn said. “We’ve definitely seen people who have lung scarring and gone home with fibrotic changes in their lungs who have continued difficulty with breathing. And there are people who three months out have lingering changes with their sense of taste and smell. That’s not a small problem. People depend on smell and taste to enjoy life.”