How the COVID Pandemic May End: Lessons From the 1918 Flu

John Whyte, MD, MPH; Howard Markel, MD, PhD

Disclosures

November 12, 2020

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  • The Spanish flu hit in the fall of 1918; a second surge occurred from January to April 1919, and a smaller one followed in the winter of 1920. Forty million people died from the flu, including 550,000-750,000 Americans. We later learned that the flu was the H1N1 strain of influenza. Secondary bacterial pneumonia was often the cause of death at that time.

  • The Black Death in the 13th and 14th centuries ranks No. 1 in terms of pandemics that wreaked havoc on people's lives and killed so many. The 1918 Spanish flu ranks second, and the COVID-19 pandemic currently ranks as a close third.

  • In 1918, cities that enacted social distancing measures early on and for a long duration were able to flatten the curve and had lower rates of morbidity and mortality.

  • Herd immunity was never developed as a measure to prevent a new virus from spreading through a particular community. It was based on active immunity and giving many adults and children immunizations.

  • The pandemic will probably end once a safe and effective vaccine is distributed across the population. We will probably be measuring the length of this pandemic in years, not months.

This transcript has been edited for clarity.

John Whyte, MD, MPH: Welcome, everyone. You're watching Coronavirus in Context. I'm Dr John Whyte, chief medical officer at WebMD.

Since March, I've been talking about COVID-19. Everybody wants to know when it will end. Can we learn anything from the Spanish flu? Many have been talking about the pandemic that occurred over 100 years ago.

To help provide some insights into how the COVID-19 pandemic may end, I've invited Dr Howard Markel. He's the director for the Center for the History of Medicine at the University of Michigan. Dr Markel, thanks for joining me.

Howard Markel, MD, PhD: Hi, John.

Whyte: Take us back 100 years. Many people are mentioning the Spanish flu, but they don't really know what was going on. Can you give us a quick history lesson of the 1918 pandemic?

Markel: Well, probably in the summer of 1918, but not necessarily, there was a short, mild wave of influenza. Since we don't have viral samples, we can't really prove that. But we do know that in the fall of 1918, influenza, which we have since discovered was the H1N1 strain of influenza, ripped through the world and particularly the United States. Then there was a second wave that resurged in January to April of 1919, which was pretty darn bad but not as bad as the fall one. By the way, there was a third surge that nobody talks about, in the winter of 1920.

By the time it was over, probably 40 million people around the world died; in the United States alone, anywhere from 550,000 to 750,000 people died. At least 10 million Americans got very sick with influenza, which, as you know, is not a common cold or a mild infection, and it makes you quite ill indeed. As we understand it, there was very little medical care. A hospital was basically a bed and maybe somebody feeding you hot liquids. There were no IVs, no antibiotics. Many people who had the flu also had secondary bacterial pneumonia, and that's what killed them because there was no medication for that.

So, it was quite virulent. No one had experience with it. And unlike most seasonal flus, which tend to affect and kill infants and very old people, it was a W-shaped curve of mortality where, in the middle V, were people from the age of 20 to 45. They were dying like flies, and that was very odd for influenza.

Whyte: Were people wearing masks? Was there social distancing and handwashing? People say there were issues with sanitation back then.

Markel: There were, of course, issues with sanitation. Not everyone had running water. 1918 is around the time in the United States when there were finally more people living in a city than out in the country. Because World War I was gearing up, there were soldiers in Army camps where they dug latrines and washed their hands from, perhaps, a well. So that was an issue.

Face masks were really in their infancy. When they were worn by a few people in places such as San Francisco, Seattle, and Los Angeles, they were made out of four or five layers of gauze. You know how porous a layer of gauze is, so it's not exactly the most definitive way to prevent contracting influenza. But there were social distancing measures that, in essence, was public health back then ─ quarantine and isolation: You isolate the ill and you quarantine those you suspect of having contact with the ill. There were public-gathering bans, the closure of bars, of amusements, theatrical events, school closures, and so on.

And in fact, we at the Center for the History of Medicine at the University of Michigan worked with the Centers for Disease Control and Prevention to do a rather comprehensive study of this. In August 2007, it was published in the Journal of the American Medical Association. We found that the cities that had social distancing measures and acted early, and did more than one or layered them, and for a long period of time, did far better in terms of morbidity and mortality than those that did not. In fact, that is the essence; that is where flattening the curve came from. It was our work that was the first historical evidence base of that concept.

Whyte: Is that the lesson that we've learned from the pandemic? Because people will say, "Well, you know what, it was so different back then." Can we really make the same comparisons you just referenced? There were issues with running water. Is it fair to make the comparisons? Everyone keeps talking about 100 years ago.

Markel: Well, as a historian, I'm well aware of the differences between now and then. That's what I do for a living. The nation was smaller, and the federal government had very little involvement at all in health issues back then. It was a very different medical context, and everything was different. What was the same was that you had big, populated cities that used these measures against an easily transmitted respiratory virus.

What's incredible is that it's not just the historical example of flattening the curve that seems to bear out; it was also other modeling studies that were developed later. In the 2009 influenza pandemic, in the early weeks in Mexico, where they did not yet know that it was not terribly lethal (they thought it was highly lethal), they too did a social distancing program and their epi curves (or epidemic curves) were identical to the ones that we found.

Sadly, we now have the best experiment of all. We have been doing social distancing measures all around the world. Nature magazine called it the one measure that saved more lives in a shorter period of time than anything ever concocted by humans, and I think that's absolutely true. If you look at the lives that were saved and the infections that were prevented when it was being done, it was working.

You have to remember that social distancing is really a form of hiding from the virus. It doesn't prevent, treat, or make you immune from the virus. It's not an issue of waves as much as that the virus is circulating and circulating widely. When you go outside (whether you're wearing a mask or not) and are interacting with more people for longer periods of time, you are increasing your risk of contracting COVID-19. It's as simple as that.

Whyte: We have to remember that with the virus, humans are the host. So it goes to your point about it: If you're hiding and can't find a host, is it just going to fizzle out and die? I wanted to ask you about how the pandemic of 1918 resolved. You mentioned that it came back in 1920. Was it herd immunity that everyone's talking about? Recognizing that it killed tens of millions of people, we didn't have a vaccine, and we didn't have treatments.

Markel: Let's be clear about herd immunity — and I'm telling you this as an old pediatrician. Herd immunity was never developed as a population kind of a measure when a virus spreads through a particular community. It was based on active immunity, giving people immunizations, giving lots of children immunizations (eg, for measles, mumps). When you immunized actively ≥ 90% of the community, then when that infection subsequently came into that community, it would not spread. The notion of letting it rip and letting a lot of people get it — first of all, you would never get levels of 60%-90%, which is what people are estimating you would need. Twenty percent simply wouldn't do it. What is the point of living in the 21st century if we're relying on 13th century methodologies of letting it spread throughout a community to protect us? Not to mention the incredible expense of taking care of people and the terrible tragedy of those who would die.

There were some people who were immune, to be sure. With flu, just like probably with coronavirus, you're not immune for that long of a period of time ─ maybe 4 or 5 months. That's why we give flu vaccines every year. Some of it is because it's a different strain, but some of it is that your immunity has worn down.

Whyte: How long do you think strains last? Because there was talk that ultimately the pandemic of 1918 really morphed into something else. Do we have a sense of how long respiratory virus strains stay active?

Markel: No, because these are issues of mutations, and where is the virus coming from? By the way, you said 1918 is very different from 1920. Well, of course it is, but what nobody's saying is that the main historical factor in these two pandemics is quite different. Influenza is a very different virus from COVID-19, with the exception that they're both respiratory-transmitted viruses.

Influenza tends to burn itself out when the cold weather gets warmer. We know that. We were hoping that was the case with COVID-19 because we saw that with SARS, for example, in 2003. But this virus does quite well in warm weather, as we're finding out. It probably will rage better in cold weather, especially if we're all indoors and crowded. Also, we use artificial forms of heat, which can cause little breaks in your mucosa, nose, mouth, and so on.

The 1918 flu probably burned itself out because the weather changed, there were people who were immune, and the virus might have just attenuated and gotten more mild. Influenza changes every year because it depends on the animal host and the human host and the level of mutations. Are those mutations more than just typographical errors in the genome?

The real story — I call this the mutation that was heard around the world — was when COVID-19 mutated from whatever animal it was a host in to the point that human beings could not only contract it but easily transmit to other humans by breathing on them. That was the killer mutation.

Whyte: You study the past, but I'm going to ask you about the future. How do you think this all ends?

Markel: Oh my, you know historians like me are uncomfortable with the whole concept of the future. That's why we live in the past.

Whyte: I know, but I can push you anyway.

Markel: As a doctor, I read prognoses all the time. You know, there's a wonderful poem by T.S. Eliot ["The Hollow Men"]. "This is the way the world ends. With a whimper, not a bang." It was written in 1925.

Will it just go away? Will it just vanish like a miracle? Well, hopefully. I think the magic bullet that will protect us and then end this nightmare will be a safe, potent, and effective vaccine. Once we do achieve herd immunity the old-fashioned way, which was based on vaccines, I think then we have a fighting chance of ending this chapter in human history. But — and there's a huge but — it's not just for industry or doctors or scientists or medicine to come up with the safe vaccine; it is all of our responsibilities here in the United States, Germany, England, and other countries around the world to roll up our sleeves and take that vaccine.

We already have an amazing amount of politicization with this pandemic, more than any I've ever seen or studied, and that's a lot of epidemics over a lot of time. We have anti-vaccinationists, we have libertarians, we have this and that. It'll be essential to have leadership from the government, in science, and in medicine who demonstrate that the vaccine is safe and effective and that we as a community all get vaccinated because it's a socially mediated disease: I can get you sick, and I won't get you sick and you won't get me sick if we're both vaccinated.

Whyte: In the history of pandemics, where does COVID-19 rank in your mind? Not just in terms of human fatalities, but also on the impact on life during that time.

Markel: That's a great dual measure. I would count the Black Death of the 13th and 14th centuries really high on my list, maybe No. 1. If you don't believe in it, go to Italy and look at all of the frescoes in various churches and so on. Then the 1918/1919 Spanish flu as No. 2 (certainly the greatest in terms of death and cases). I would put COVID as a close third. Maybe it's not No. 1 or 2, but it's certainly up there in the top 5, and a lot depends on how long this goes on.

Whyte: Certainly not a ranking we want. Like other pandemics that you've studied, in general, do you think it will last a period of 2 years, 3 years, a year? What's a historical reference?

Markel: Well, we don't have a historical reference because we're using a very old pandemic (eg, the Black Death), and there was no medicine. The doctors who did exist then had a completely different idea of what caused infectious diseases. Even with the 1918 flu, you had germ theory. But it was still a theory, and you had no medications to end it and certainly no vaccines.

I wrote a piece for The New Yorker magazine in August about just that, and I said we would be measuring this not in weeks or in months, but in years. Could it be only a year? I hope. Could it be more than that? It may. As I said, it really depends on when we get this vaccine.

Whyte: Dr Markel, I want to thank you for providing your insights, and for giving us a history lesson so we can learn from the past and not repeat the mistakes.

Markel: George Santayana said, "Those who ignore the past are destined to repeat it." That keeps people like me gainfully employed.

Whyte: Thank you for sharing your insights. And thank you for watching Coronavirus in Context.

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