Swine Flu Kills, Sometimes

Essay / by Rob Dunn /

For swine flu, history and recent advances in evolutionary biology provide only a partial blueprint. Ultimately, any recourse must rely on incomplete data and imperfect knowledge.

Illustration: Joe Kloc

In March, the president of the United States appeared before reporters to discuss the reappearance of swine flu. Worried about a pandemic, he announced the appropriation of funds sufficient to inoculate “every man, woman, and child in the United States,” amounting to nothing short of the largest public health campaign in US history. Disease biologists working closely with the president supported his decision (at least most of them). What The New York Times called “the virus that caused the greatest world epidemic of influenza in modern history” had returned. And so the cost of inaction, the president argued, was too great to countenance.

That was 1976. Gerald Ford was president.

In the 1976 outbreak of swine flu — a strain of the influenza virus endemic in pigs but which has mutated across multiple species and become transmissible from human-to-human — it seemed as though, unless dramatic action was taken, a repeat of a catastrophic pandemic from earlier in the century was imminent. In that pandemic of 1918, 50 to 100 million people died, and as many as millions died in each of a dozen earlier flu pandemics. Over the last few days we have found ourselves faced with local eruptions of a newly mutated strain of swine flu. Cases have been reported in Mexico, Texas, New York, Canada, and elsewhere. Schools have been closed, flights cancelled, and advisories issued. The number of cases is growing (though not nearly as fast as the news articles, worry, and tweets). It seems that on the horizon, just as in 1976 and for that matter 1918, looms the specter of a new pandemic. Blogs have already begun to ask, apocalyptically, “Will we, too, all die?”

In 1976, President Ford stuck his thumb in the dam. His army of inoculators did their work (vaccinating approximately 25 percent of the US population, all told), and everyone waited. Nothing happened. And then people began to get sick. From the inoculations. The program was cancelled and the flu pandemic never materialized. In fact more people died of complications from Guillain-Barré syndrome induced by the vaccinations than from the flu itself, an estimated twenty five versus one.

In the contrasting stories of the worldwide pandemic of 1918 and the non-pandemic of 1976 one hopes for an instructive parable. But there isn’t one. The 1976 and 1918 outbreaks represent two data points within a broad continuum of possible scenarios, which depend on our action but also on the vagaries of evolution. We track the new cases and make educated guesses (projections, as scientists like to call them), like news commentators calling the election. The law of averages suggests that our own fate, in the days that come, will be somewhere in between the 1976 and 1918 scenarios. But such is imprecise speculation, and of course there is no guarantee. Viruses have an unpredictable streak — a kind of evolutionary idiosyncrasy — that makes them, from an intellectual perspective, fascinating, difficult, and enigmatic. It is far from clear, for example, why flu viruses are seasonally cyclical; a mystery that is actively discussed, but which few would call resolved. Viruses live and die and evolve over hours. But we live and die as a consequence and as much as these peculiarities matter, they are still beyond our ability to predict.

And so without a clear forecast, we can just look to the different flu outbreaks to see what each suggests about what we could have and should have done. Even today it is still difficult to say what led to the unusually virulent behavior of the 1918 strain. New research helps to understand which of the genes of the 1918 virus made it particularly aggressive; but why those genes came together just then and whether the same genes will be associated with virulence in the future is unknown. Also unknown is whether current medical care and public health programs could have contained the outbreak. When millions of lives are at stake, extreme responses can be warranted. But the 1976 outbreak tells us that there are consequences to reactionary responses based on deficient understanding. Although the costs of the inoculations were relatively minor (500 sick; 25 dead), the case still demonstrates the unpredictability of contagion and what little we knew about the epidemic behavior of viruses. With perfect knowledge we could of course tailor our response to the future, to the fate of the strain. But we don’t have perfect knowledge. If there is a pithy lesson here, it is one of our ignorance. In looking into the future, we face uncertainty.

Yet we must make decisions, even when the data are uncertain and the future even more so. In the weeks and months that come, we must decide relatively quickly what to do to combat this resurgence of swine flu: We will call experts into the room and try to come up with a solution. We hope we’re smarter or luckier than we were in 1976, or for that matter 1918. In many ways we are. We can now reconstruct, in intimate detail, the evolutionary history of specific flu viruses. We can now model many aspects of pandemics. And yet the situation today is, in many respects, similar to the one in 1976. We don’t know enough yet about the behavior of viruses, the emergence of pandemics, and the measures that slow them, speed them up, or simply leave them as they would have been. Some models suggest that cancelling airline flights reduces the numbers of cases of flu; others suggest that such measures simply slow the course. Some models suggest face masks affect the spread of the disease, others don’t. The uncertainty of what is known confronts the urgency of a crisis. And in those moments, ultimately, no previous historical example tells us precisely what to do.

So over phone calls and meetings at big wooden tables, world leaders and top-ranking officials at the CDC and WHO make critical judgments — synapses firing, bodies tired and mortal — based on data that are still out. And we all, the susceptible billions, wash our hands and wait.

 —  Rob Dunn is assistant professor in the department of biology at North Carolina State University and author of Every Living Thing.

Originally published May 1, 2009

Tags contagion genetics pandemics policy

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