Avian flu has so far proved more fizzle than firecracker: It has killed fewer than 150 people, compared with the 35,000 Americans who die yearly from ordinary flu. But the scientific frenzy it sparked is paying off with an array of insights into how the next real epidemic might emerge.
1. New pathogens can incubate slowly, then change rapidly. Sporadic outbreaks of the H5 family of influenza viruses have appeared among birds in Scotland, South Africa, Mexico, and Pennsylvania since the 1950s. Those outbreaks remained localized, however, and triggered few if any human infections. Then the current virus, called H5N1, appeared in 1996 in China. This version was able to spread widely—and this one could kill.
2. Diseases spread in ways researchers don't fully understand. How did H5N1 zoom so quickly across continents? "The short answer is that we don't know enough," says Laurence Gleeson of the United Nations Food and Agriculture Organization. A strain from Qinghai Lake in China jumped to Turkey in October 2005 and reached Iraq by the beginning of 2006, suggesting that migratory birds may be involved. People transporting infected poultry are probably also contributing to the spread.
3. Countries most vulnerable to outbreaks are often the ones least able to deal with them. The current crisis most likely stems from the rapid growth in poultry production in the developing world, which has outstripped the capacity of governments to manage animal diseases, Gleeson says. Up to two-thirds of families in Vietnam—hit hard by the outbreak of H5N1 among birds—raise chickens at home. A backyard poultry ban could cost the poorest residents there up to 25 percent of their income.
4. We need better surveillance. Jean-Paul Chretien of the Department of Defense's Global Emerging Infections Surveillance and Response System suggests that the international community fund a system of labs modeled after U.S. military research laboratories. These labs would bolster surveillance and help contain emerging diseases in developing countries. Such a system might take a decade or more to set up.
5.We are at the mercy of viral evolution. Researchers in Japan and the Netherlands found that H5N1 doesn't bind to cells in the upper respiratory tract, so it probably doesn't spread well among humans through coughing or sneezing. Almost 50 years after it surfaced, the H5 strain remains primarily a threat to birds.