Stopping Enza

Back when kids passed the time by reciting rhymes about viral illnesses, the children of the 1918 flu epidemic jumped rope to this little ditty: "I had a little bird / Its name was Enza. / I opened the window / And in-flew-Enza!" It's appropriate that Enza was a bird, because bird flu (or avian influenza) has been a problem since well before you ever read a headline about swine flu. Now, British scientists think they've come up with a way to stop avian influenza in its tracks. Instead of using a vaccine, they put the roadblock right into birds' genes.

Influenza is widespread in wild birds, which usually carry the virus without becoming sick. But a highly  deadly type of avian influenza has been touring Asia for the past several years, often leading nations to slaughter millions of domestic birds at a time. Aside from killing poultry, the virus occasionally leaps to humans, where it can also be deadly. So far, bird flu doesn't spread easily between humans. But since influenza is always mutating, scientists worry that avian influenza is one tweak away from becoming the next human pandemic.

The researchers inserted DNA into chickens that let them produce, in effect, a decoy for influenza's machinery to latch on to. The piece of machinery in question is an enzyme called polymerase. It's supposed to attach to the virus's genetic material and chug along, like a train on train tracks, replicating that genetic material to make new viruses. But the chicken decoy mimics influenza's latching-on spot, so the polymerase attaches to the decoy and sits there uselessly.

When the genetically altered chickens were infected with bird flu, they...died as usual. But! The infected chickens did not efficiently spread the flu to the birds around them. Usually, avian influenza sweeps through groups of birds mercilessly. But the genetically altered chickens were less contagious than usual, sparing the lives of some of their coop-mates.

It's not clear exactly how the decoy DNA made the chickens less contagious. The study shows, though, that genetic engineering might be able to prevent deadly infections. Vaccines are impractical for preventing the flu in chickens--since new strains of influenza appear so often, they'd presumably need a new shot every year, just like we do. But the genetic decoy in this study is general enough to snag any type of avian influenza. If research in this area goes forward, genetic engineering could be the key to controlling flu outbreaks on farms--and preventing future pandemics in humans.