If a flu pandemic strikes the U.S., the government plans to hand out millions of doses of the antiviral drug Tamiflu to reduce the death toll.
Scientists say that's a reasonable approach, since there's no vaccine for bird flu, and Tamiflu appears to do some good.
But the drug is no panacea, says Dr. Anthony Fauci, the director the National Institute of Allergy and Infectious Diseases.
In testimony before the House Commitee on International Relations, Fauci said, "I want to caution the committee that we cannot equate stockpiling and availability of Tamiflu with preparedness. We have no hard scientific data of how well this antiviral will perform under the conditions of a pandemic."
Fauci told the committee that Tamiflu doesn't cure even everyday flu.
"What this antiviral does is diminish the duration of symptoms by approximately a day and a half," he said.
That's because Tamiflu doesn't kill the flu virus. It just slows it down so the body's immune system can catch up.
Even so, scientists like Dr. Frederick Hayden of the University of Virginia School of Medicine are more positive about Tamiflu.
"The public needs to recognize that there are limitations with our current agents, that these are not magic bullets," Hayden says. "But at the same time these drugs can provide a great deal of benefit."
For some people critically ill with bird flu, that could mean mean the difference between living and dying.
Hayden says one of the limitations of Tamiflu is that it needs to be taken within a day or two after a person gets sick.
"Once someone someone is in a desperate situation with advanced pneumonia," he says, "there's no evidence that antiviral treatment really does any good."
That's a problem with bird flu because patients may not get diagnosed until they have been ill for several days.
Hayden says another limitation of Tamiflu is that ordinary flu viruses have shown they can develop resistance to it.
"We've known for some years that Tamiflu-treated patients can shed resistant virus," he says. "It's been seen in about one in five children, for example, treated for conventional influenza.
More recently, scientists have found signs that bird flu virus also can develop resistance to Tamiflu. A recent study said described two patients in Vietnam who died after the virus became resistant.
Hayden says that in spite of Tamiflu's limitations, it makes sense for governments to purchase large quantities of the drug. One reason is that even a small decrease in the severity of a flu pandemic would be worth the billions of dollars countries are spending on Tamiflu.
"You need to balance that against the economic impact that a major epidemic could have," he says.
Fauci, the government scientist, agrees that Tamiflu could make a difference — if a pandemic struck soon.
But in his testimony before Congress, he pointed out that it will be years before the U.S. stockpile is complete.
"The strategy is ultimately to have 75 million treatment courses to cover 25 percent of the population," Fauci said. "We have assurances from the company that we will get to 20 million treatment courses by December of 06 and the 75 million by the summer or Spring of 07."
That may be optimistic. Roche, the company that makes Tamiflu, is scrambling to fill orders. And many other countries placed their orders for the drug well before the U.S. did.