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Spanish Flu Redux?


Apocalypse, pestilence, death. As I head back to work after a late-summer vacation, those words are on the tip of my tongue. Now before your mind drifts too far afield, this is not a synopsis of the time spent with family, or even my in-laws—although some have used similar words to describe my mother’s cooking. Rather, these are the descriptors of my vacation reading.

Summer Reading

I started the week relaxing contentedly with Cormac McCarthy’s “The Road.” I chose this book in part because I noticed that it soon will be released as a movie, but mostly because it had won the dustiest-book-in-my-office-reading-pile award. This tale of a young boy and his father traversing a post-apocalyptic America was shocking and surreal. I couldn’t help but interchange images of my 2-year-old son, Greyson, and me out on that road fighting for our existence. In my personal fictional account, I continuously, and heroically, MacGyver my way across a burned-out and treacherous landscape with death-defying adeptness—all the while Grey unknowingly totters, drooling and muttering in tow.

The Spanish flu pandemic of 1918-1920 infected 500 million people and killed as many as 100 million worldwide. HULTON ARCHIVE/GETTYIMAGES

The Spanish flu pandemic of 1918-1920 infected 500 million people and killed as many as 100 million worldwide.

Reality, of course, would paint us in substantially different roles, with mine involving the lion’s share of muttering and drooling, leaving Grey wishing the apocalyptic dealer had dealt him his mother instead.

Next up, “The Last Town on Earth,” by Thomas Mullen. I don’t recall how this book got into my reading pile, but I’m glad it did. The story is set in the fictional city of Commonwealth in 1918. The small, isolated mill town makes the drastic decision to stanch the tide of Spanish flu by cutting itself off from civilization through a self-imposed quarantine.

It is here, on p. 98, that I was sidetracked by a family member’s question—“Do you think this swine flu will be as bad as the Spanish flu?” I was asked shortly after being inquired about my reading choice. “Of course not,” I replied knowingly, moments before realizing I didn’t know. In fact, I didn’t have the faintest idea—not because it’s tough to divine the future, but because I realized I had little more than a passing knowledge of the famous flu that raked the world early last century. And with that, I was off on my final vacation reading session—a quest to slake my thirst for influenza knowledge.

Flu Pandemic

The Spanish flu pandemic of 1918-1920 was the first of three to hit in the 20th century. It took its name not from its site of origin (debated but generally felt to be the U.S., Kansas specifically), but rather from the fact that Spain, a neutral country in World War I, had the most uncensored lines of communication, so the most credible news of the disease came from that country. This provided the false impression that Spain was the only—or at least most dramatically—affected country. Like today’s swine flu, the Spanish flu was an H1N1 influenza. To sate your inner microbiologist, this means the virus exhibits the first of 16 subtypes of hemagglutinin (H) and nine subtypes of neuraminidase (N). Generally, only H1, H2, H3, and N1 and N2 affect humans, and tend to cause mild disease in otherwise healthy populations, killing the immunocompromised, the very young, and the very old. This typically results in a case-fatality rate of about 0.1% and 250,000 to 500,000 deaths worldwide annually.

It is estimated that 500 million people—one-third of the world’s population at the time—were infected. The mortality rate was from 10% to 20%, resulting in 50 million to 100 million deaths. Put another way, the Spanish flu killed 5% of humanity.

The Spanish flu, however, was different. For reasons that are not entirely clear, the Spanish flu struck in two waves. The first wave, in the spring of 1918, induced typical flu-like illness with generally mild outcomes, except for the immunocompromised. The second wave was unusual for two reasons. First, it began in the late summer of 1918, rather than the typical winter pattern seen in North America. Second, it was much more deadly, inducing what has been termed a cytokine storm. This immunological avalanche produced more severe disease in the immunopotent young, healthy populations—resulting in its unprecedented mortality in this cohort. In fact, upward of 99% of all Spanish flu deaths were in people younger than 65.

In the end, the pandemic left a broad swath of destruction in its wake. It is estimated that 500 million people—one-third of the world’s population at the time—were infected. The mortality rate was 10% to 20%, resulting in 50 million to 100 million deaths. Put another way, the Spanish flu killed 5% of humanity.

It did so rapidly. Nearly 1 million people died per week in the first 25 weeks of the second wave. To put it in perspective, it took HIV 25 years to reach that number. Thus, historians have termed the Spanish flu “the greatest medical holocaust in history.”

And then as quickly as it commenced, it abated. For example, in Philadelphia, there were about 5,000 flu deaths in one week in October 1918, yet a month later, the virus had nearly disappeared from the city. It’s not clear why this happened, but prevailing theories postulate that either the medical community got better at managing its mortal complications (e.g., bacterial pneumonia), or the bug itself mutated to a less virulent strain.

Is the Swine Flu our Spanish Flu?

On June 11, 2009, the World Health Organization (WHO) declared that the current H1N1 flu virus had reached pandemic status. This novel H1N1 serotype appears to be a direct descendent of the Spanish H1N1 subtype, but the new strain also combines genetic material culled from swine and birds reassorted in a manner that results in limited innate human defenses. And like the Spanish variant, it appears this new strain is hitting earlier in the year than usual and disproportionately affecting the young, with about two-thirds of U.S. deaths coming in the 25- to 64-year-old demographic.

So can we expect hundreds of millions of deaths from swine flu? Probably not. The WHO has been cautious to note that the upgrade to pandemic status was based on the rapidity and ease of spread, not the lethality of the virus. Furthermore, the Centers for Disease Control and Prevention (CDC)—which publishes a wonderful weekly update called FluView (—notes that while the number of doctor’s visits for influenza-like illnesses through mid-August is unusually high, the rates of hospitalizations and proportion of deaths attributed to pneumonia and influenza are low and within normal limits for this time of year. Further, the virus continues in its original form, meaning it has not mutated, become more resistant to antiviral drugs, or been altered from the viruses selected for the 2009 vaccine.

So while we certainly must brace for the worst, I feel comfortable in the answer I provided my family member. I also am confident that Grey won’t be quarantined or left to roam the barren Earth anytime soon. TH

Dr. Glasheen is associate professor of medicine at the University of Colorado Denver, where he serves as director of the Hospital Medicine Program and the Hospitalist Training Program, and as associate program director of the Internal Medicine Residency Program.

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