While watching the last few episodes of the PBS Masterpiece hit series “Downton Abbey,” I kept waiting for somebody — anybody — to get sick.

For the years 1918 and 1919 were marked in Britain — as in the United States and elsewhere around the world — with one of history’s most virulent and deadly flu pandemics. By the time the pandemic had run its course, it had taken the lives of at least 50 million people, many more than had been killed by fighting in World War I.

Finally, last Sunday, the flu pandemic made its appearance on the north Yorkshire country estate of the Earl and Countess of Grantham. But it did so in a sanitized way, it seemed to me. Wouldn’t more members of the household have fallen ill and died? Where was the fear (and face masks)? And wasn’t 1919 a little bit late for the flu to hit the Grantham estate, especially since Downton had been housing convalescing soldiers? Soldiers were, after all, one of the main conveyers of the disease.

To get some answers, I spoke with Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy, and Richard Danila, an epidemiologist with the Minnesota Department of Health. Danila is one of several co-authors of a fascinating 2007 article in the journal Public Health Reports on how the 1918-1919 pandemic affected the cities of Minneapolis and St. Paul.

Neither Osterholm nor Danila was familiar with the “flu” episode of “Downton Abbey,” so I had to describe to them how the pandemic was depicted on the show.

That depiction, it turns out, may have been slightly more accurate than I thought. But it still had some problems.

The question of timing

To begin with, it wasn’t entirely unreasonable to have the flu sweep through Downton in April 1919. The pandemic came in three waves, explained Osterholm. The first wave arrived in the spring of 1918; the second (and most deadly), in the fall of 1918; and the third, in the early spring of 1919.

I suspect that the writers of “Downton Abbey” brought the illness to the Grantham household during the third wave because having it hit while the war was still going on would have made the plot line too complicated (and it’s pretty convoluted as it is).

But if a steady stream of soldiers had been coming in and out of Downton during 1918, the flu probably would have descended upon the household earlier, Osterholm said.

“The highest morbidity and mortality in the military [from the flu] was in the fall of 1918,” he pointed out.

Danila agreed. “I would imagine that if they had troops coming back [to the house] to convalesce during the war, the flu would have swept through them,” he said.

Particularly deadly for young adults

The fact that only one young person in the Downton household succumbed to the disease (or even got ill from it) is also suspect, for the 1918-1919 strain of the H1N1 influenza virus was particularly contagious — and deadly — among young adults.

“That was the age group most impacted,” explained Osterholm. “The median age of death was in the mid-twenties.”

So, the “Downton Abbey” writers were reflecting what really happened by having the youngest of their three chosen flu victims — a woman in her twenties — die.

It’s just that other young people would probably have died on the estate, too.

Death came fast

The show also accurately depicted the surprising speed with which the 1918-1919 influenza virus killed its targets. In one scene, Downton’s doomed young flu victim, Lavinia Swire, is sitting up in bed and talking coherently with her fiancé. A few hours later, she’s dead.

“That did happen,” said Osterholm. “There were clearly those deaths that took several days, but there were also deaths that took place within 24 hours.”

And, as in the show, a doctor could tell who was going to die soon. “When a doctor would see a patient really blue, they knew they had this very severe pulmonary disease, and that it predicted death within 24 to 48 hours,” explained Osterholm.

An absence of fear

And what about the fact that none of the characters in last Sunday’s episode seemed at all fearful about being around someone with the flu? After all, by 1919 almost everybody knew that the illness was highly contagious and had a very high death rate. (That wasn’t true in 1918, when governments hid the severity of the pandemic from the public out of a fear that it would hurt morale during the war.)

As Danila points out in his article, people in the Twin Cities were walking around with facemasks by the fall of 1918. Even doctors were scared. Some declined to help with public-health efforts to care for the sick.

“I didn’t see [last Sunday’s “Downton Abbey”] episode,” said Danila, “but it’s concerning to hear that no one [in it] was afraid, because people were very afraid at the time.”

In more rural areas of the United States, he added, residents put up border crossings to keep people out. And in the Twin Cities, officials periodically closed down schools, churches, theaters and other public venues in desperate attempts to stall the spread of the virus.

Why accuracy matters

OK. So who cares if “Downton Abbey” gets medical matters wrong? After all, it’s just a TV show.

Well, some of the points — like whether the flu would have been more likely to hit Downton in the fall of 1918 than in the spring of 1919 — probably don’t matter.  But the sanitization of the pandemic — the playing down of how widespread and devastating and fear-instilling it was — does.

“It really was a major event in modern human history,” said Danila. “Outside of wars, there weren’t many events seen like it. So to downplay it at all is wrong.”

“Cleaned up” depictions of the pandemic may also contribute to complacency, he added. If we misunderstand what happened in 1918, we won’t be fully prepared for the next major pandemic, which many pubic-health professionals believe is long overdue.

Now, if we could just get the writers of “Downton Abbey” to also be a bit more realistic about Matthew’s injury. As one spinal cord specialist has noted, it’s unlikely Downton’s heir would ever had made it back from the front with such an injury. And if he had, he probably would have developed bed sores that would have quickly become infected and, in those pre-antiobiotic days, killed him. Or he would have developed a bacterial urinary-tract infection that would have killed him.

But then there wouldn’t be a Series Three.