The world is divided by war. Influenza outbreaks smolder in livestock herds and bird flocks for years. The public is deeply skeptical of the value of medical interventions. Public health agencies offer misleading advice and are focused only on keeping the public calm. There is a shortage of qualified medical professionals, with no end in sight.
No, this isn’t 2025—it’s 1918. In the pivotal book The Great Influenza, historian John Barry lays out the conditions that primed the population of the U.S. that year for one of the worst plagues in history and acted like so much dry tinder just waiting for a spark. That spark exploded into the conflagration of the 1918 influenza pandemic, which killed an estimated 50 million people worldwide and left many others disabled.
A little more than a century later, now is perhaps as good a time as any to ask the question: How prepared are we for another influenza pandemic? On the surface, this is an easy question to answer. Modern medicine and public health have advanced far beyond 1918. Whereas the scientists of that era struggled to identify the germ that caused the pandemic, we live in a time of genomic sequencing and global infectious disease surveillance, of mRNA vaccine technology and antiviral medications. Our governments have pandemic preparedness plans, stockpiles of vaccines and drugs, and, having dealt with the COVID pandemic, experience with contact tracing and isolation.
On supporting science journalism
If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
Other conditions, however, are eerily similar to those of 1918. Geopolitical crises crowd public health concerns off the front page of newspapers. A dangerous influenza strain, in this case the H5N1 avian flu virus, has recently been circulating freely within poultry flocks, spreading widely in livestock herds in the U.S. and causing infections in farm workers. False lessons drawn from the COVID pandemic have driven public skepticism of medical information to all-time highs. Public health agencies sometimes offer contradictory and falsely soothing messages, further eroding their credibility. And after five years of COVID, hospital systems are stretched thin, and burnout and staffing shortages have thinned the ranks of the doctors and nurses who will be on the front line of the next pandemic. Making matters worse, the Trump administration’s interventions over the past two months have gravely weakened surveillance of and control over the virus’s spread.
The global response to the COVID pandemic offers little solace. In late 2019, as SARS-CoV-2, the virus that causes COVID, gripped China, infectious disease surveillance failed across much of the rest of the globe. Western governments faltered right out of the gate at limiting the spread of the virus—contact tracing detected fewer than 2 percent of all COVID cases in the U.S., for example. The pandemic response plan was ignored, and molecular tests were too few and too late. There were not enough high-quality masks, and antiviral drugs for COVID had not yet been developed. The plan was to “flatten the curve,” but in practice, hospitals ran out of beds, intensive care units ran out of oxygen and morgues ran out of space. While lives were saved by social distancing and eventually vaccines, millions also died needlessly across the globe. They were victims of poor pandemic policy and a sluggish public health response, as well as misinformation and disinformation about vaccines and other health measures.
But that was—and still is—a different pandemic, one caused by a coronavirus rather than influenza, with a far lower death rate for acute cases and a somewhat different set of challenges. In contrast, when pandemic influenza hit in 1918, it killed 3 to 5 percent of the world’s population, and around half of those deaths were in young and healthy people. A pandemic similar in scale today would leave 200 to 400 million dead.
Revisiting the Deadly 1918 Pandemic
It’s hard to imagine now, but the 1918 influenza was far worse than the flu we know. Although many affected people experienced a severe bout of seasonal flu—fever, chills, body aches and headaches, followed by recovery—some fared a lot worse. As Barry puts it, these people “came with an extraordinary array of symptoms, symptoms either previously unknown entirely in influenza or experienced with previously unknown intensity.” Those symptoms included agonizing joint pain, burning pain above the diaphragm, subcutaneous emphysema (which occurs when pockets of air accumulate just beneath the skin), ruptured eardrums, kidney failure and severe nosebleeds.
Scientists today think that 1918 influenza mainly killed in one of three ways: through cytokine storms, acute respiratory distress syndrome (ARDS) or secondary bacterial pneumonia. (If these terms sound familiar, it’s because COVID killed in much the same way in an immunologically naive population in 2020.) Cytokine storms occur during an extreme immune response in which too many immune signals in the form of cytokine proteins are released in a short period of time and cause severe tissue damage. When a cytokine storm hits the lungs, the result is ARDS, “a virtual scorching of lung tissue,” according to Barry. The lungs of people with ARDS fill with fluid, which gums up oxygen transfer to blood vessels and eventually causes organs throughout the body to fail. Some survivors of the 1918 influenza were left with profoundly weakened immune systems and fell victim to bacterial pneumonia in the weeks that followed infection. Any of these three conditions can land a person in the intensive care unit today and have a high risk of death. Similar effects were seen with hospitalized patients during the 2003 SARS outbreak; one of us (Filiatrault) was the emergency physician on duty when the first case of SARS in Vancouver was detected.
Unfortunately, we gain very little protection against pandemic influenza from our past infections and vaccinations against seasonal flu. A hallmark of pandemic influenza viruses is that they are just different enough from preceding strains that they evade the body’s immune defenses almost entirely. Influenza has a segmented genome, which increases the chance that its genetic material, or RNA, is shuffled into new forms through recombination when two different influenza viruses infect the same host. And back-and-forth transmission between humans and animals lets the virus mix and match parts of its genome. The recombination route is a pretty efficient way to get to a brand new influenza virus, and it’s what led to the 1918, 1957, 1968 and 2009 influenza pandemics.
At this point, if a seasonal flu virus particle, which has evolved to spread efficiently between people, recombines with an H5N1 avian flu virus—which has historically killed about half of those it has infected, although this number has varied widely from year to year—the resulting virus could be at once fairly deadly and highly transmissible.
The U.S. is currently in the midst of the worst seasonal flu outbreak in more than a decade, and in addition, H5N1 has been ravaging poultry flocks. If the risk of recombination between human and avian influenza from poultry wasn’t enough, there’s also a threat from cows. Two versions of the virus are circulating in dairy herds as well, and one of the strains is particularly concerning. So far, the mortality rate for H5N1 this year seems to be low, but that low mortality rate is far from guaranteed in a dynamic situation such as this.
Imagining a Flu Pandemic Today
What would happen if a flu strain capable of causing a pandemic hit today? Let’s walk through a scenario in which an outbreak is spreading quickly through, say, New York City, and see how things would go. First, we know that contact tracing and surveillance would likely fail in such a situation—it failed during the early days of COVID, and it has failed already for some cases of H5N1. In some human cases of H5N1, the source of transmission is unknown, and there is evidence of asymptomatic transmission between people. And the Trump administration’s recent actions have created dangerous new vulnerabilities.
The White House’s plan to lower egg prices emphasizes alternatives to culling infected flocks, but that could increase transmission among hens and to humans working with those flocks. Bird flu surveillance efforts have been undermined by turmoil at the U.S. Department of Agriculture, where 25 percent of staff members in an office responsible for coordinating the bird flu response were fired last month—though at least some termination letters were later rescinded—and at the Epidemic Intelligence Service of the Centers for Disease Control and Prevention (CDC), which faced similar cuts (that were later reversed) around the same time. The shutdown of the U.S. Agency for International Development, which supported the control of infectious disease worldwide, and the directive to limit communication between the CDC and the World Health Organization has only made things worse at a critical time.
Vaccines are unlikely to completely deflect the course of an oncoming pandemic either. Although H5N1 vaccines exist in the nation’s stockpile, they are not yet approved by the Food and Drug Agency. Additionally, they would only cover a fraction of the world’s population, and their efficacy against a brand-new mutant strain of H5N1 is unknown. While mRNA vaccines have been talked up, it would take months to ramp up production of them—they would arrive too late to nip an incipient pandemic in the bud. Falling rates of vaccine coverage for seasonal flu suggest that vaccine uptake would be an uphill battle made harder by changes to the CDC’s communication policy. Although the U.S. government has contracts in place for a pandemic influenza vaccine, those contracts are now being reconsidered.
The situation is worse for antivirals. There is good reason to question the efficacy of the one flu drug that is stockpiled, oseltamivir (Tamiflu), even against seasonal flu, and how well it will work against a pandemic strain is completely unknown. Cuts to medical research and a shift away from infectious disease research could hardly come at a worse time.
The one thing that we do know works against influenza is masking. Increased masking and physical distancing during 2020 led to the first known extinction of a seasonal flu strain. Once again, though, there may not be enough masks to go around, and not everyone will use them. It doesn’t help that public health guidance for influenza emphasizes handwashing and vaccination, and it mentions masking only as an additional preventive strategy, if at all. To date, there is little evidence that handwashing reduces the spread of influenza, which transmits through the air.
When it comes to the ways in which we can expect pandemic influenza to kill—ARDS, cytokine storms and secondary bacterial pneumonia—medicine doesn’t handle these deadly threats that much better than it did a century ago. Malnutrition—a predisposing factor for death in 1918—remains a concern worldwide and in the U.S.
This past experience, along with the fact that infectious disease surveillance for H5N1 has failed already and the time lag between infections and hospitalizations, during which a virus can spread, suggests that if an outbreak of H5N1 were to erupt in New York City tomorrow, it would be spreading in the community by the time the first cases showed up in hospitals. Without contact tracing in place, not much could be done to keep the outbreak from growing exponentially. With medical infrastructure stretched thin, hospitals would overflow eventually, and refrigerated trucks would be back. Commercial flights would scatter the virus across the globe far more efficiently than the troop ships and trains of 1918. Within a week, the sparks of the next pandemic would land all around the planet. And as we watched the world go up in flames, all that would be left for public health agencies to offer would be soothing reassurances that it is not yet time to panic.
While it is never time to panic, it is never too soon to prepare. Sadly, it is relatively clear to anyone paying attention that—plans on paper notwithstanding—we are every bit as vulnerable to pandemic influenza now as we were a century ago.
Those who forget history, the saying goes, are condemned to repeat it. At this point, the next influenza pandemic is not a question of if but when. And the “when” gets closer with every new H5N1 infection in humans. There are practical steps that can be taken to make us safer: public health officials can implement better infectious disease surveillance and biosecurity, share public health information in a more transparent way, make sure stockpiles of masks and other safety equipment are replenished, plan for surges in hospital utilization, and update guidelines on airborne spread and the importance of masking in preventing transmission. Rather than downplaying potential risks, public health officials should focus on mitigating them now.
