Five years after Covid-19 shut down activities all over the world, medical historians sometimes struggle to place the pandemic in context.

What, they are asking, should this ongoing viral threat be compared with?

Is Covid like the 1918 flu, terrifying when it was raging but soon relegated to the status of a long-ago nightmare?

Is it like polio, vanquished but leaving in its wake an injured but mostly unseen group of people who suffer long-term health consequences?

Or is it unique in the way it has spawned a widespread rejection of public health advice and science itself, attitudes that some fear may come to haunt the nation when the next major illness arises?

Some historians say it is all of the above, which makes Covid stand out in the annals of pandemics.

In many ways, historians say, the Covid pandemic — which the World Health Organization declared on March 11, 2020 — reminds them of the 1918 flu. Both were terrifying, killing substantial percentages of the population, unlike, say, polio or Ebola or H.I.V., terrible as those illnesses were.

The 1918 flu killed 675,000 people out of a U.S. population of 103 million, or 65 out of every 10,000. Covid has so far killed about 1,135,000 Americans out of a population of 331.5 million, or 34 out of every 10,000.

Both pandemics dominated the news every day while they raged. And both were relegated to the back of most people’s minds as the numbers of infections and deaths fell.

J. Alexander Navarro, a medical historian at the University of Michigan, said that in the fall of 1918, when the nation was in the throes of the deadliest wave of the 1918 flu, “newspapers were chock-full of stories about influenza, detailing daily case tallies, death tolls, edicts and recommendations issued by officials.”

During the next year, the virus receded. And so did the nation’s attention.

There were no memorials for flu victims, no annual days of remembrance.

“The nation simply moved on,” Dr. Navarro said.

Much the same thing happened with Covid, historians say, although it took longer for the virus’s harshest effects to recede.

Most people live as though the threat is gone, with deaths a tiny fraction of what they once were.

In the week of Feb. 15, 273 Americans died of Covid. In the last week of 2021, 10,476 Americans died from Covid.

Interest in the Covid vaccine has plummeted, too. Now just “a measly 23 percent of adults” have gotten the updated vaccine, Dr. Navarro noted.

Remnants of Covid remain — lasting financial effects, lags in educational achievement, casual dress, Zoom meetings, a desire to work from home. But few think of Covid as they go about their daily lives.

Dora Vargha, a medical historian at the University of Exeter, noted that there had been no ongoing widespread effort to memorialize Covid deaths. Instead, with Covid, “people disappeared into hospitals and never came out.”

Now it is only their friends and families who remember.

Dr. Vargha called that response understandable. People, she said, do not want to be “dragged back” into memories of those Covid years.

But some, like those suffering from long Covid, can’t forget. In that sense, she sees parallels with other pandemics that, unlike the 1918 flu, left a swath of people who were permanently affected.

People who contracted paralytic polio in the 1950s described themselves to Dr. Vargha as “the dinosaurs,” reminders of the time before the vaccine, when the virus was killing or paralyzing children.

Every pandemic has its dinosaurs, she said. They are the Zika babies living with microcephaly. They are the people, often at the margins of society, who develop AIDS.They are the people who contract tuberculosis.

But despite the pleas from those who cannot forget Covid and who seek more research, more empathy, more attention, the more pervasive attitude is, “We don’t need to care anymore,” said Mary Fissell, a historian at Johns Hopkins University.

That sounds so callous, and yet, said Dr. Barron Lerner, a historian at NYU Langone Health, in the world of public health “there are always people who are left behind — damaged or still at risk.”

“It’s hurtful” for people to be shunted aside, Dr. Lerner said. “Their lives are altered. The attention you feel their situation warrants is downplayed.”

But, he added, “on a realistic basis, there are any number of things to study.” Resources are limited, he noted, adding, “it can make sense to move on.”

One aspect of the Covid pandemic, though, is still with the nation, and seems to be part of a new reality: It has markedly changed attitudes toward public health.

Kyle Harper, a historian at the University of Oklahoma, said he would give the biomedical response to Covid an A-plus. “The rollout of vaccines was incredible,” he said.

But, he said, “I would give the social response a C-minus.”

Dr. Lerner had the same thought.

Few medical experts, he said, expected so much resistance to measures like masks, quarantines, social distancing and — when they became available — vaccines and vaccine mandates.

With Covid, he said, “compared to other pandemics, the amount of pushback to standard public health practices was remarkable.”

“That sets Covid apart,” he said. Public health measures that had worked in the past were rejected.

Some of the pushback was reasonable, he said, like objections to wearing masks outdoors. But the spurning of public health measures was widespread and politicized.

Dr. Navarro agreed and said the contrast with 1918 was striking.

“In 1918, there was an abiding respect for science and medicine that seems lacking today,” he said. There were pockets of resistance to measures like masking and avoiding large groups. But for the most part, he said, people complied with public health advice. And compliance was divorced from politics.

World War I also played a role in the messaging, Dr. Navarro said, which may have bolstered adherence.

“Public health orders and recommendations often purposely used the same language that was used to drum up support for the war effort,” Dr. Navarro said. The authorities, for example, asked people “to cover their coughs and sneezes so as not to gas their fellow citizens as the doughboys were being gassed by the Germans.”

Dr. Lerner contrasted the Covid response to the response to the polio vaccine.

The polio vaccine underwent preliminary testing, and then widespread testing, in the 1950s, with broad public acceptance.

With Covid, “faith in the scientific process got lost,” Dr. Lerner said.

That does not bode well for the next pandemic, Dr. Harper said.

“There’s going to be another pandemic,” he said. “And if we have to fight it without public trust, that’s the worst possible response.”