One Year Later: 5 Lessons from the H1N1 Pandemic

It was a year ago that the term H1N1 entered the American consciousness, stamped in 72-point tabloid type. In April 2009, researchers at the Centers for Disease Control and Prevention (CDC) discovered that two children in California had been infected with a new strain of influenza virus — originally dubbed “swine flu” but eventually and more accurately known as H1N1 — even as Mexican health officials grappled with major outbreaks of a new flulike illness. By the end of the month, with new cases popping up in New York City, Canada and Europe, officials had come to realize they had a global emergency on their hands.

On April 27, 2009, World Health Organization (WHO) director-general Margaret Chan announced that the agency would raise the global flu pandemic alert level from 4 to 5 — the first concrete step toward acknowledging that the world was caught in the grip of its first new pandemic in more than four decades. “This virus has the potential to spread very widely,” said Chan at the time.

(See “The Year in Health 2009.”)

Within weeks, the H1N1 virus was spreading around the world, and by June the WHO had raised the alert level again, officially declaring an influenza pandemic. Since most people had no immune protection against the H1N1 virus, which had been simmering in swine populations for years before jumping into human beings in Mexico, it spread rapidly.

U.S. cases piled up in late spring, and both the sick and the “worried well” flooded hospitals, taxing health care resources. Schools shut down, sometimes for weeks, to stem the spread of the disease, leaving millions of schoolchildren — and their parents — stranded at home. In other countries, the response was more severe: in Mexico, the government banned public gatherings; in China, travelers from affected regions who showed signs of flu were quarantined.

From the start, the vast majority of H1N1 cases seemed relatively mild, but officials still had to work to keep the population from panicking. “This is obviously a cause for concern,” said President Barack Obama on April 27, 2009. “It’s not a cause for alarm.”

(See pictures of the swine flu outbreak in Mexico.)

As it turned out, Obama was right — almost painfully so. Pharmaceutical companies had crashed an H1N1-vaccine-production program, and governments around the world (including Washington) had drawn up hasty plans to fend off a potential “second wave” of H1N1, which they feared could turn the upcoming fall flu season into a public-health disaster.

Yet catastrophe never came, and the total U.S. death toll from H1N1 — about 13,000 people over the past year — was considerably smaller than the 36,000 people who are estimated to die each year from the regular, seasonal flu. Millions of doses of H1N1 vaccine expired unused on doctors’ shelves, and health officials are now under fire for overhyping what eventually seemed like a harmless bug. So, was H1N1 much ado about nothing?

See more about swine flu.

Not quite. Understanding why H1N1 was, and remains, a legitimate public threat and how health officials could have handled it better will help when the next new virus inevitably makes its way into our bloodstreams.

Here are five key lessons from the 2009 H1N1 flu pandemic.

1. H1N1 was more serious than the death toll suggested.

At the start of the H1N1 pandemic, officials could already see the virus was easily transmissible — cases were accumulating fast, and it took only a few weeks for the virus to reach nearly every corner of the world. But while researchers knew from past pandemics that a new flu virus like H1N1, against which humans have no immunity, could spread quickly, what they could not immediately gauge was whether it could also be deadly. Some past pandemics had been relatively mild, while others, such as the 1918 flu, which killed as many as 100 million people worldwide, had not. At the outset, there was no way to know which kind of virus H1N1 would turn out to be.

In hindsight, the 2009-10 pandemic looks relatively mild — certainly much milder than the initial media panic might have led us to expect. Still, a closer inspection of H1N1 shows that it was no trifle. Unlike seasonal flu, which tends to kill the elderly and those with underlying health conditions, H1N1 proved disproportionately dangerous to the young, the healthy and the pregnant.

A recent study published in the journal BMC Infectious Diseases found that more than 75% of H1N1 cases recorded in the early months of the pandemic occurred in people under age 30, with the highest proportion in those ages 10 to 19. And when researchers at the National Institutes of Health measured the impact of H1N1 in estimated American life-years lost — which gives more weight to deaths among the young — they found that it was at least as serious as a typical flu year; at its worst, it hit levels seen in the pandemics of 1957 and 1968. Its death toll may have been lower than feared, but H1N1, especially in the early months, stressed the U.S. health care system with large numbers of young, sick flu patients, and ventilators and antivirals were sometimes in short supply. “H1N1 was an enormous challenge,” says CDC director Thomas Frieden.

2. The pandemic you prepare for may not be the one you get.

When H1N1 struck, the WHO and other health agencies had already been preparing for a new flu pandemic — just not the one that actually arrived. Rather than from the pork farms of Mexico, officials thought the next pandemic would emerge from the yards of Asian chicken farms. In the years since H5N1 avian flu began simmering in Southeast Asia in 2003, scientists and doctors had monitored the virus closely, waiting for it to mutate to the point that it could spread easily from person to person. The virus had already proved itself deadly — it has killed nearly 300 people to date — but the question was when it would become transmissible.

See more about swine flu.

It hasn’t yet. While attention was focused on bird flu in Southeast Asia, H1N1 was evolving in swine in Mexico. In a way, the locus was a stroke of luck — the Mexican government reacted about as well as a country could to a sudden outbreak, and unlike China in its initial response to the SARS outbreak of 2003, it did not hide the presence of the new virus.

But the opening of an unexpected front caught health officials off guard. The lesson here isn’t that we should stop worrying about bird flu or Southeast Asia — still the birthplace of most new flu viruses — but that in a globalized, heavily populated world, new viral threats can come from anywhere.

3. Prevention means surveillance.

Before H1N1 became known as H1N1, it was popularly referred to as “swine flu” because scientists determined that it contained mostly pig flu genes. (That’s not surprising: pigs can be infected with both avian and human flus and are an ideal genetic mixing bowl.) The term swine flu was confusing, since the virus was circulating in people and was not being transmitted by swine (unlike the avian flu H5N1, which is passed primarily by birds), but it was instructive. It reminded us that new flu viruses begin not in people but in animals and that the first humans to be affected tend to be those who are in close contact with animals.

That means the right kind of virological surveillance might be able to detect potentially dangerous viruses while they’re still in animals and even stamp them out before they establish themselves in people. The problem is that animal health gets only a fraction of the funding and talent devoted to human health — the World Organization for Animal Health is a poor cousin to the World Health Organization — even though the two realms are intertwined.

Over the past seven years, H1N1, H5N1 and SARS have all emerged out of animals to infect and kill human beings. That trend must be stemmed. One smart idea is the Global Viral Forecasting Initiative, an NGO that monitors populations that are highly exposed to animals — such as hunters in Africa — in hopes of detecting new viruses as early as possible. “You need earlier and earlier capacity not to overlook the clinically evident cases that can reveal a new outbreak and give you maximum time for preparation,” says Institute of Medicine president Dr. Harvey Fineberg, who will lead an independent panel review of the WHO’s response to the H1N1 outbreak.

4. Vaccine manufacturing is outmoded, but vaccines are not a panacea.

The good thing about the H1N1 vaccine was that it wasn’t technically difficult to create — vaccine makers designed and produced it the same way they do regular, seasonal flu vaccines. The problem was the timing. By the time H1N1 emerged in the spring of 2009, production of the next batch of seasonal flu vaccines was already well under way, so drug companies had to hustle to establish a separate production line to get the new H1N1 vaccine manufactured and available for the upcoming flu season.

At the same time, global vaccine production was in general decline, and the U.S. had very little vaccine-manufacturing capacity left. Worse, there were no official channels of pandemic-level vaccine distribution. Washington promised millions of doses of H1N1 vaccine in time for the start of flu season in October 2009, but distribution was repeatedly delayed while federal, state and local officials struggled to coordinate how best to hand out the doses. If H1N1 had been truly severe, those delays could have cost lives.

But the major hindrance is the way vaccines are currently manufactured — grown in individual doses in batches of chicken eggs. While flu vaccines take months to produce, flu viruses spread around the planet in a matter of days. So unless the U.S. and other wealthy nations upgrade their vaccine-production strategies (experimental cell-based techniques may be able to churn out new vaccines much more quickly) and add more capacity, we’re guaranteed to struggle to defend against the next pandemic. Vaccines may represent the best line of defense against a new flu virus, but not if they’re too slow to do any good.

Still, it bears noting that vaccines are not the only defense against a flu virus. Other, simpler strategies — like hand washing, sanitation and distancing measures like keeping sick people at home — can quickly stem the spread of a virus.

See more about swine flu.

Some evidence also suggests vaccines may not even be as effective against flu viruses as advertised. A review of the scientific literature by Tom Jefferson, an epidemiologist at the Cochrane Collaboration in Britain, finds little scientific data to support the effectiveness of flu vaccines in reducing infection or death. Jefferson told TIME in February that “we don’t know what protection, if any, [flu] vaccines offer.”

Jefferson’s work should at least remind health officials that the focus on vaccines must not blind them to other cheap and effective means to blunt the spread of a new virus — especially if we’re still making vaccines the slow, old-fashioned way.

5. It all boils down to communication and trust.

The main concern going forward should not be the way health officials responded to the last pandemic but how we will respond to the next one. And that may prove worrisome: the perception that officials overhyped and overreacted to the H1N1 pandemic may make the public less inclined to react appropriately the next time around. The fact that vaccination rates in the U.S. were still fairly low during the latest flu season — Harvard researchers estimate that 6 out of 10 adults were not vaccinated — indicates an abiding skepticism toward public health. But while we got off relatively unscathed this time, next time we may not be so lucky.

The only way to defuse public skepticism is for health officials to communicate better what they know about an outbreak — and even more important, what they don’t know about it. Washington officials did an admirable job putting out information in the early days of the H1N1 pandemic, but they were less successful at putting that information in context. There wasn’t enough explanation of what a “pandemic” really meant: that it referred only to the transmissibility of the new virus, not its virulence.

Leaving interpretation of the data to the media, whose coverage tends to swing between extremes, is not a good idea. In an age of Twitter and transparency, there’s no substitute for official honesty. “Communication in 2010 is a really tricky situation,” says Anne Schuchat, director of the CDC’s National Center for Immunization and Respiratory Diseases. “This was the first pandemic done in the age of the Internet.” Chances are it won’t be the last — but if we learn from H1N1, at least we’ll be prepared.

See TIME’s Pictures of the Week.

See the Cartoons of the Week.