Think of the next influenza pandemic like an earthquake. We know it's coming; it's just a matter of when and how bad it'll be. Biostatistician Ira Longini wants to make sure we're ready. Crunching data at Emory University's Rollins School of Public Health, Longini creates computer models to test strategies for squashing the bug before it gets out of control. He has good reason to worry: The relatively mild Hong Kong flu pandemic in 1969 killed 34,000 people in the US. Today, because of increased international air travel, the same virus would spread faster and kill even more people. The total economic hit could be more than $150 billion. So, uh, how do we avoid that?
WIRED: Why does the flu keep coming back to haunt us?
LONGINI: The flu virus goes through genetic drift. It has point mutations, and you get slight variants. They're different enough that you don't have good cross-immunity, and newly reassorted viruses, with different proteins on their surfaces, tend to be quite a bit more virulent. H3N2 is the common flu. Avian influenza - bird flu - is H5N1. And it looks like H5N1 will eventually reassort with a human virus, probably H3N2, and gain the capacity to spread person to person.
Why can't we stop that from happening?
Because it could be a different avian flu in the Netherlands, for example, that ends up being the pandemic strain, or it could be a swine flu in Kansas. It's hard to predict exactly. We start with a virus's natural history, which tells us what happens to infected people, and a whole set of behavioral parameters that tell us how populations are connected. The final piece is an estimate of vaccine and antiviral efficacy. Then we can model how it will spread and how we will deal with it.
Well then, how will we deal with it?
If neuraminidase inhibitors, which are flu antivirals, are used aggressively at the site of emergence, then we would have a fairly good chance of controlling the flu - maybe 70 to 80 percent - or at least slowing it enough so that there'd be time to make vaccines. Ultimately, the way to stop pandemic flow is to develop a good vaccine and distribute it to the population. Even with enough vaccine for just 20 to 30 percent of the population, we can optimize it by concentrating on the high-spreading population, which is almost always schoolchildren. You tend to get a lower overall death rate than you would from covering only high-risk people. But ethically, you have to protect high-risk people, regardless of what optimization theory tells you.
Was the 2004 vaccine shortage a sign of things to come?
Oh, absolutely. We're going to have more and more shortages. We have only two suppliers of flu vaccine for the US. One of them had a contamination problem, and we lost half our supply almost overnight. The only way we could really increase production is if the government guaranteed the manufacturers that it would buy 150 million doses every year. If the pandemic starts in Asia, by the time it gets to the US it'll be very difficult to control without vaccine. You'll probably have multiple entry points around the country and outbreaks all over the place from a virus well adapted to human transmission. It's much more effective to stop it at the source.
- Greta Lorge
credit:Annemarie Poyo
Bug hunter: Longini predicts more vaccine shortages.
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