The last pandemic was a ‘quiet killer.’ Ten years after swine flu, no one can predict the next one

The cryptic phone call came on a Monday. The Centers for Disease Control and Prevention was holding an important teleconference for a few reporters. I should dial in.

When the time came, just a handful of reporters were on the line. Also there: the CDC’s top flu experts. They sounded worried.

Two unrelated children from southern California had tested positive for flu infections caused by viruses that normally sicken pigs. This could have been a fluke, but from the unusual nature of the call and from the tension in the voices of the experts, it was clear that the CDC officials thought it might be something else: an influenza pandemic.

That teleconference took place on April 20, 2009. Over the next seven weeks it became apparent that any fears they had had been well-founded.

On June 11, 2009 — 10 years ago today — the World Health Organization declared that the swine flu virus we now simply call H1N1 had indeed triggered a pandemic, the first time in four decades a new flu virus had emerged and was triggering wide-scale illness around the globe.

Since it started circulating in the spring of 2009, H1N1 has infected about 100 million Americans, killing about 75,000 and sending 936,000 to the hospital, the CDC estimates. Another virus, H3N2, is responsible for more infections, but “in terms of the severity, H1 is kind of this quiet killer,” said Dr. Daniel Jernigan, head the CDC’s flu division.

In the hands of Hollywood, pandemics tend to be of the one-size-fits-all variety. They unleash massive chaos and spread at lightning speed, as health officials in hooded biohazard suits rush to distribute vaccinations. And in real life, flu pandemics, which tend to strike only a few times each century, could be that terrifying. But, a decade onward, the experience of H1N1 is a reminder that it’s impossible to know from the get-go how a pandemic will play out.

Science currently has no way to predict when pandemics will occur. The fact that there were 41 years between the 1968 pandemic — known as the Hong Kong flu — and the 2009 pandemic doesn’t mean the next will take another 30 years or so to materialize. There is no pattern; flu pandemics happen when they happen, and pandemic planning is ever ongoing.

In the case of H1N1, the public health world was steeling itself for a potentially catastrophic outbreak. Just six years earlier, officials began to respond to a very dangerous bird flu virus called H5N1, first in Southeast Asia and then beyond. It was deadly to chickens and other poultry but — and this was unusual — it was also occasionally infecting people. When it did, the outcome was sobering: More than half of people known to have been infected with the virus died from the infection.

The number of people infected with H5N1 was small, but it stoked fears that this fearsome flu might be readying itself to cause a pandemic. In its place, however, arrived H1N1.

It was distantly related to other H1N1 viruses that had circulated among people for most of the 20th century. In fact, pigs acquired H1N1 decades before from people. But this new virus had evolved in a way that helped it unlock the mysteries of the human respiratory tract and sicken people.

Fortunately, though the infection could be severe, it was not devastating in most cases. A study published in 2013 suggested between 123,000 and 200,000 people globally may have died as a result of the 2009 H1N1 pandemic.

This was certainly not nothing. But it was also not what people had feared would be in store, and it was a substantially lower death toll than was seen in the 1957 and 1968 pandemics, which each killed about 1 million people at a time of lower global populations. In fact, the H1N1 death toll was lower than the global death toll for typical flu seasons, as estimated by the WHO.

But just looking at the number of deaths masks the full impact of the pandemic, because the people who died were younger than those influenza normally claims. (The elderly, whose immune systems had seen viruses similar to this one long ago, weathered the pandemic pretty well.) A group of researchers who analyzed the deaths based on years of life lost concluded the pandemic’s toll in the United States was at least as bad as an average H3N2 flu season and potentially as severe as the 1968 pandemic.

That picture of the 2009 pandemic was only painted after the fact. At the time, the WHO faced pressure from some key member countries not to declare H1N1 a pandemic at all, because of the apparent lack of severity of the situation. The outbreak seemed, well, wimpy after years of warnings of a bad pandemic. Supply chains didn’t break; global air travel was not disrupted.

Still, the WHO made a formal pandemic declaration.

Doing so automatically activated pre-negotiated pandemic vaccine contracts that a number of wealthy countries had with vaccine manufacturers — and a number worried they didn’t need what they were on the hook to buy. Germany, Spain, Switzerland, and France told their suppliers they didn’t want all the vaccine they had ordered. In France’s case, the government told manufacturers it wouldn’t take possession of about half of the 94 million doses it had contracted to buy.

The European Parliament later criticized the WHO response as excessive. At least one politician alleged the event was a windfall for pharmaceutical companies that made pandemic vaccine. That argument ignored the fact that flu vaccine takes months to make; if the WHO and countries with preexisting pandemic vaccine contracts had waited to see how severe the outbreak was before ordering vaccine, they’d have had no chance of getting any in time for it to be of use.

As it turned out, they pretty much didn’t anyway. The vaccine took longer than expected to produce.

In the U.S., the Health and Human Services Department estimated in July 2009 that 120 million doses would be available by October. By late October, only 17 million doses had been shipped — and fewer than that had been administered. By the time vaccine was becoming available, infections had peaked and flu activity was declining sharply.

Whenever there’s a major outbreak there are postmortems. Among the key lessons learned from 2009 was it was not enough to tell countries a pandemic had started. They also needed real-time guidance on how severe it seemed to be.

It was also clear that a WHO-established program designed to guarantee low-income countries access to some pandemic vaccine needed more work. In 2009, the WHO had asked vaccine-purchasing countries to donate a portion of their supplies as the vaccine came out of the pipeline. But the reality was that by the time the agency had vaccine to redistribute, the threat had largely dissipated and with it demand for vaccine.

Now the global health agency requires vaccine manufacturers to commit to donate a portion of their pandemic vaccine production in real time in exchange for getting access to the flu viruses the manufacturers use to make seasonal flu vaccine. The WHO recently reported it had signed 13 such agreements with manufacturers, commitments that would give it access to an estimated 400 millions doses of pandemic vaccine that it would distribute to countries in need in the next pandemic.

So will things work better the next time there’s a pandemic? Without knowing how much severe illness the outbreak will cause, it’s almost impossible to venture a guess. It’s worth noting, though, that many of the knock-on effects that a disruptive event like a bad pandemic could cause — the stress it would place on the always fragile supply of key medications, for instance — remain as threatening today as they did a decade ago.

That said, there are some promising developments on the horizon, CDC’s Jernigan said. An explosion in the development of medical tests that work with smartphones raises the specter of a rapid flu test that people could be used at home. Positive results would be sent via phone to doctors’ offices; prescriptions for antiviral drugs would be issued to pharmacies — all without an infected person having to visit a doctor.

A new antiviral drug, Xofluza, which is taken in a single dose, could also have a big impact in the next pandemic. The drug is fast-acting and reduces the amount of viruses that people sick with flu emit — potentially lowering the risk they would infect others. But there are concerns flu viruses could develop resistance to the drug quickly, so its role in a future pandemic is unclear.

At the end of the day, the main tool for fighting flu is vaccine. And with most flu vaccine still made — in hen’s eggs — the same way in 2019 as it was in 2009, and 1968, and 1957 for that matter, there’s every reason to worry about how quickly flu vaccine would be ready when the next pandemic strikes.