As health experts around the world prepare for a possible bird flu pandemic, one area of focus is the antiviral drugs that would be relied on to treat people once they have contracted the disease.

The antiviral drug that experts believe will be most effective against bird flu is Tamiflu, a so-called neuraminidase inhibitor.  The drug attacks an enzyme on the surface of the virus and stops it from spreading to other cells. 

Tamiflu is not an antibiotic, which only works against a bacterial infection.  It is also not a vaccine, which must be given before a person becomes infected.  Instead, Tamiflu is used as a treatment that will work most effectively if administered within the first few days of the onset of the sickness.

Health experts believe drugs like Tamiflu will work against the bird flu in humans because they have already been used extensively to treat annual outbreaks of seasonal flu, which occur mostly in autumn and winter. 

At a news conference to discuss the seasonal flu, Health and Human Services Secretary Mike Leavitt said the U.S. government is interested in both Tamiflu and another antiviral drug called Relenza for use against bird flu.

"We are stockpiling Relenza and Tamiflu, both, for the purpose of a potential pandemic," he said.

Tamiflu can be taken orally, while Relenza comes in powder form and must be inhaled.  Secretary Leavitt did not say how many doses of the two drugs have been stockpiled, but he acknowledged that the U.S. government considers Tamiflu easier to use than Relenza.

Swiss company Roche is the sole manufacturer and patent-holder of Tamiflu, which is suddenly in short supply worldwide.  In coming weeks, Roche will be meeting with at least four generic drug companies to discuss allowing them to manufacture the drug and help increase production.

Bird flu started in Asia.  The disease has led to the deaths of millions of birds, which were either infected or killed to prevent the spread of the virus.  Only about 60 humans have died so far, but health experts say there are signs that the bird flu virus could mutate into a virus that could spread easily to humans. 

Secretary Leavitt emphasized that, although there have been no reports of bird flu in the United States, either among birds or humans, Washington is getting ready for a possible pandemic.

"We're preparing," he explained.  "We're preparing by building stockpiles of antivirals, producing a vaccine, improving our international surveillance network and increasing preparedness at the federal, state and local level."

He added that the Bush administration will soon unveil what he called a "strategy for pandemic preparedness," which will involve more detailed plans of a potential U.S. response.