A Flu Strain Goes Kerflooey

First, the good news: As flu seasons go, this one isn't bad--at least as far as the overall numbers are concerned. This season, 11,000 cases of influenza have been confirmed in the U.S., on a par with the caseload at this time for the past few years. The vaccine, designed to protect against the three flu strains that researchers predicted would cause the most illness this season, seems to be a pretty good match for what ended up being the most common strain. And there's enough vaccine to go around.

Now the not-so-good news: you can never be complacent about a virus as fond of mutating as influenza is. We're always just a few random genetic shifts away from a possible pandemic. Researchers at the Centers for Disease Control and Prevention (CDC) last year documented for the first time that one of the many viral components that make up a common flu strain, known as H1--which also happens to be a descendant of the same virus that fueled the pandemic of 1918--was resistant to the popular antiviral drug oseltamivir, a.k.a. Tamiflu. In the flu season--October to May--of 2007-08, 12% of circulating H1 subtypes were resistant to the drug; this season, 98% of them are. Interestingly, the mutation does not appear to be driven by overuse of the drug. In fact, rates of oseltamivir resistance are higher in nations like Norway where there is little use of the drug, and lowest in countries like Japan where the antiviral is prescribed heavily.

That means that other medications, like zanamivir, a.k.a. Relenza, or prescribing oseltamivir in combination with other drugs is still an option. But the spread of a resistant strain raises the specter of a pandemic--brought on by a flu virus that is highly contagious and invulnerable to nearly all our medical efforts.

That's why flu experts around the world are keeping their microscopes poised to detect just such mutations. Under the leadership of the World Health Organization (WHO), four flu labs--in London, Tokyo and Melbourne and at CDC headquarters in Atlanta--are picking apart flu viruses sent to them throughout the season from doctors treating infected patients. "This is certainly far and away better than the system that existed before, where we weren't doing real-time surveillance to see what was changing, such as resistance," says Nancy Cox, director of the WHO-CDC Collaborating Center for Influenza in Atlanta.

What can we nonexperts do? Get a flu vaccine every year. No shot is 100% effective, but getting vaccinated gives you a good chance of lessening your symptoms--and thus your infectiousness--should you get slammed with the oseltamivir-resistant strain. There's also hope that a promising antibody--which researchers discovered in February--that binds to a nonmutating part of the virus could one day provide lifetime protection in a single shot against practically all versions of the flu. No more annual flu vaccine and no more worries about the next pandemic. Until then, we just have to hope that the virus doesn't evolve too far ahead of our ability to keep up.