1. On the verge of disaster?

2. Mixing and matching genes

3. Responding to infection

4. Science fights flu

One way to combat the spread of avian influenza is to control poultry markets more tightly. That can be tough. During the recent appearance of H5N1 flu, some countries proved more cooperative than others. Photo: Food and Agriculture Organization.

The much-feared avian influenza strain H5N1 appears in gold, growing in a laboratory culture of dog kidney cells (green). Photo: CDC Public Health Library.

Epidemics would be simpler if they were just a matter of microbes causing disease. Instead, epidemics result from the interaction of microbes with social, economic, political and medical conditions. If that's true, then epidemics can be eased by changing the conditions that promote them.

We're not going to discuss every aspect of how human organizations confront new diseases. But a few examples, from this and other outbreaks, show what happens behind the scenes when a dangerous disease hoves into view.

International cooperation
Because diseases ignore borders, public-health workers have internationalized the struggle against disease. The central player in responding to outbreaks is the World Health Organization, which uses formal and informal mechanisms for detecting new threats.

A fast, smart response can turn back a deadly infection. For example, the largest outbreak of Ebola, a bleeding disease, was controlled in 2001 by an international collaboration directed by WHO's Global Outbreak Alert & Response Network.

WHO relies on help from national health agencies. David Daigle, a spokesman for the CDC's National Center for Infectious Diseases, told us that CDC has already sent seven people to Asia to collect bird flu samples and information on how it is spreading. Speed matters, Daigle says. "Sometimes they leave very quickly. A lot of our folks had been talking to Vietnam and WHO ... and eventually the invitation came for a WHO team. Our guys were standing at the door, and off they went."

National health efforts
As China proved with its laggardly response to the SARS epidemic last year, national health agencies don't always pull their weight. Another example arose during 2003, when Indonesia's government consistently denied that H5N1 was killing its poultry. Even though somewhere between 4.7 and 16 million birds have died from the virus, the government continues to collect and bury dead chickens, rather than slaughter entire flocks, which is the accepted way to control the spread of H5N1.

"Without government action to eradicate the disease, unscrupulous farmers have been selling infected chickens and chicken meat for months," wrote the Los Angeles Times (see "Inaction Blamed ..." in the bibliography). BTW, chicken meat can be infectious unless thoroughly cooked, although you'd probably have to give the bird a strong sniff to get the virus into your breathing apparatus.

Vaccination campaigns
Aside from natural immunity from past infections, vaccines are the finest flu fighters. Unfortunately, the vaccine front offers little solace at this point. First, no vaccine can protect against H5N1. Second, supplies of regular flu vaccine ran dry in December, just weeks after the CDC's head publicly pushed flu shots.

This matters, because while regular flu vaccine cannot give immunity to H5N1, it could still be beneficial, especially to anyone who is exposed to avian flu from poultry. Reducing the number of more familiar (and therefore less deadly) flus reduces the chance that anyone will simultaneously get infected with avian and human flu strains. That's when the two strains might be able to swap genetic material, creating a deadly bird virus that's good at infecting people.

Flu vaccine ran short because industry made only 83 million doses for a U.S. population of 291 million. And the flu season started out with some fairly nasty (but still human) strains, increasing interest in the shot. Curiously, while the CDC promotes the flu shot, it's up to private industry -- in the United States -- to decide how much vaccine to make. The decision is based, not on the health impact, but on profit-and-loss considerations: Vaccine-makers were stuck with unsold merchandise during the previous flu season, so they cut back on production for 2003-04.

Social and economic conditions
When epidemiologists investigate disease, they focus on how it spreads. A primary source of human exposure to bird flu seems to be the huge live-bird markets in Asian cities. While these markets are a longstanding tradition, scientists consider them frequent-flier miles for bird flu. With thousands of birds and thousands of customers, virus found in feces or feathers can find a ready home in another bird -- or in a person. But while the Hong Kong market has made some changes to reduce viral spread, more needs to be done, Webster wrote. "Because of cultural mores, politics and entrenched traditions, however, the Hong Kong and New York markets will likely remain open until another pandemic erupts." Only then, he says, would society consider finding less virus-friendly ways for getting birds to the frying pan (see "Influenza" in the bibliography).

Deaths from infectious diseases fell in the United States during the 20th century. The spike shows the 1918 influenza pandemic, which killed more than 20 million people, include about 500,000 Americans. Graph: CDC.

Political preparations
While a vaccine against H5N1 virus would be a great thing, there are other ways to prepare for avian flu. For example, antiviral drugs played a major role in containing a recent bird flu outbreak in Holland that infected the eyes of about 800 people. The drugs are useful for treatment, but even more for preventing flu's spread. In a logical world, since it would take 18 months to gear up production, large stockpiles of antiviral drugs would be assembled in advance of the epidemic that many experts consider inevitable. Two types of antiviral drugs, the neuraminidase inhibitors and the adamantine family, work against some types of influenza.

But the stockpile is empty, Webster told a teleconference in November. "No country has yet invested in stockpiling. It's been thought about, talked about, but talking doesn't get it done." Although a stockpile would cost billions for the United States alone, the drugs on hand today would immediately run out during the start of a pandemic, and the danger could be long past before antiviral production was ramped up.

How can science fight flu?

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