From this point on, avian influenza experts increasingly refer to containment as a strategy that can delay but not prevent a future avian flu pandemic.

No warnings had been issued against visiting any country when this article went to press, but influenza experts have been advising travelers to take precautions.

Yesterday, at the World Health Organization headquarters in Geneva, a panel of influenza experts recommended inclusion of the California strain in next season's vaccine.

But the panel has been wrong only once in the last 10 years, Dr. Stöhr, the health organization's top influenza expert, said in a telephone interview.

But even though virtually all leading influenza experts in this country contributed to the blueprint, none discussed the need for high-security laboratories, Dr. Patriarca said.

Finding the secret of the 1918 flu has been the ultimate goal of Dr. Taubenberger's meticulous work, which has riveted the attention of influenza experts.

Many influenza experts and health officials fear a worst-case occurrence in which a person becomes infected with both an avian influenza virus and a human one.

He is an internationally known influenza expert at St. Jude's Children's Research Hospital in Memphis.

The avian strain has affected what influenza experts say is "an unprecedented" number of bird species.

All 1.5 million chickens there were slaughtered within three days, a step some influenza experts have credited as preventing a global epidemic.