"Bird Flu" Could Be Slowed at the Source, Study Says

Brian Handwerk
for National Geographic News
August 3, 2005

Amid fears that a possible "bird flu" pandemic could kill millions, a new study examined potential ways to slow such an outbreak at its source—and buy precious time for vaccine production.

Some results are encouraging, but success remains dependent on improved surveillance, widespread drug availability, effective quarantine, and good old-fashioned luck.

Experts from U.S. universities and Thailand's Ministry of Health used a computer model to simulate an outbreak in rural Southeast Asia—the most likely place for a new, more deadly avian influenza strain to emerge.

"If we end up with a pandemic like [previous catastrophic pandemics], we'll have a lot of people dead," said study team member Elizabeth Halloran, professor of biostatistics at Emory University in Atlanta, Georgia.

Halloran added that the simulations show that it should be possible to contain an outbreak at its source. But the results are unpredictable. "We have shown in these simulations that—even given the same [hypothetical] situation—sometimes when we intervene it's successful and sometimes it's not," Halloran added.

A global influenza pandemic like the infamous "Spanish flu" of 1918 and 1919 could leave tens of millions dead. Many experts warn that the world is unprepared, and overdue, for just such a catastrophe. The leading candidate to spark such an event is H5N1, a strain of avian influenza, or bird flu.

Pandemics occur when viruses mutate into forms that are easily passed from human to human and that cannot generally be stopped by the human immune system.

H5N1 is found primarily in domestic and wild birds but also in mammals, such as cats and pigs. The virus has yet to become easily transferable between humans.

Model Mimics Spread of Asian Outbreak

The study team used data from the Thai 2000 census and from previous studies of social networks in Thailand's rural Nang Rong district. The researchers attempted to replicate the ways in which an outbreak would spread through a rural population of some 500,000 people.

The model simulated a flu's movement and person-to-person interactions at all levels of society, from "close contact" environments—like homes, schools, and workplaces—to more casual contacts in places such as markets and temples.

Beginning with a single infected person, the model projected numerous scenarios of viral spread and development. The spread scenarios were largely based on the average number of people that each infected person is likely to infect.

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