They don't like it when visitors to the new Strategic Health Operations Center at the World Health Organization call it "the war room." It's not the right metaphor for an organization whose purpose is to preserve life and which also happens to be headquartered in a neutral country. Instead, they call it the "SHOC room."

Nevertheless, this underground space filled with electronic maps and video screens is where WHO may someday launch the equivalent of a commando attack against pandemic influenza.

Curiously, the man who will command it doesn't have a lot of confidence the assault will succeed.

"The issue for us is that influenza will be very difficult to slow down and stop," said WHO physician Michael Ryan, as he sat in the quiet operations center this month after a meeting that brought 600 experts here to plan for a possible global epidemic of flu.

"Our primary advice to countries," he said, "is to prepare for this eventuality: emergence, silent or otherwise, of a pandemic virus that spreads worldwide more quickly than we have the capacity to contain, in a series of waves, with a very high attack rate on the population."

He is one of many flu experts who believe the world is closer to a pandemic now than anytime since 1968, when the Hong Kong flu killed about a million people worldwide. There were two other pandemics in the 20th century, the 1957 Asian flu, which killed more than 2 million, and the epochal Spanish flu of 1918, with at least 50 million deaths, according to a recent recalculation.

A surgeon by training who has his specialty's typical assertiveness, the 41-year-old Ryan runs WHO's Global Outbreak Alert and Response Network (GOARN). Over the next three months, he plans to assemble a medical strike force that could be sent on six hours' notice to anyplace a potential pandemic emerges.

But his job -- and that of many others at WHO -- is to also prepare the world for the strike force to fail. That means countries should have written plans for what to do in the event of pandemic influenza, which probably would cause illness in one-quarter of the population over a few months and kill an unpredictable number.

Specifically, governments need to decide beforehand what to tell their citizens about how to protect themselves; whether to ban gatherings or travel; how to ration hospital beds and medical equipment; and how to dispose of a potentially large number of bodies.

About 60 percent of nations have pandemic plans. The U.S. government released its 396-page document, with more details to come, this month.

The current threat is influenza A/H5N1, a strain of avian influenza that emerged in Hong Kong in 1997, was extinguished and emerged again. Since late 2003, it has killed 150 million birds and, by WHO's official count, has infected 125 people and killed 64.

It does not have the ability to be easily transmitted from person to person. If it were to gain that capacity through genetic mutation or reassortment with another flu strain, however, H5N1 would probably cause a pandemic, as virtually everyone on Earth is susceptible.

No flu pandemic has ever been stopped or even controlled. GOARN's attempt would be the first.

The network is, in Ryan's term, a "global fire brigade." It has about 400 people from nearly 200 government agencies, charitable organizations and academic institutions. They have agreed to go to a disease outbreak on a moment's notice if their particular expertise is needed. Since 2000, GOARN has investigated reports of 900 outbreaks. Many were false alarms or were handled by locals. The network responded to more than 50.

Unlike a fire brigade, however, GOARN's goal is to train people to put out their own fires. Its purpose ultimately is to help developing countries in particular, where most outbreaks occur, acquire the skills and technology to do their own disease surveillance; recognize suspected cases quickly; confirm the diagnosis with laboratory tests; and, not least, treat the ill and protect the caregivers and the public.

The network just finished fighting an outbreak of Marburg hemorrhagic fever, an ebola-like infection, in Angola. The first case was detected March 21. At the outbreak's height, more than 130 non-Angolans were working on it. Before it subsided, the outbreak totaled 374 cases and 329 deaths.

The first team sent to try to contain pandemic flu might start small: two epidemiologists; two laboratory scientists; three logisticians to handle electricity, food, equipment and accommodations; one data management and computer expert; a communications officer; possibly a water and sanitation engineer; possibly an anthropologist or "social mobilizer"; and a few others whose function would depend on details of the outbreak.

The response would also almost certainly require personnel to move and help distribute antiviral drugs, to treat or prevent infection. WHO has 3 million treatment courses of oseltamivir (Tamiflu) donated by its maker, Roche, and is negotiating to buy more.

Ryan is trying to be realistic. "Most of the communicable disease . . . we generally have a confident sense that if we intervene rapidly, we can deter disease on site. That's our basic principle," Ryan said. "We know through contract tracing, isolation, quarantine, infection control and good surveillance that we can put the fire out."

Influenza is different. When fully adapted to people, it might be humankind's most contagious pathogen. Nevertheless, Ryan is no nihilist. He remembers SARS.

Early in the 2003 outbreak of severe acute respiratory syndrome, the infection appeared to be moving like flu. There were individual superspreaders and large clusters of infections. But the SARS virus turned out to be fairly hard to transmit, and the epidemic was halted with the old-fashioned tools of outbreak control.

When fully adapted to humans, by contrast, influenza is easily passed by breathing and coughing, and the virus can survive for hours on surfaces such as doorknobs and subway poles. Its victims tend to be up and around -- and infecting others during their peak infectiousness early in the illness. The virus thrives in cool, dry environments of the sort found indoors in winter.

H5N1 does not have those traits now. If it acquires them, they may not come rapidly or suddenly. Instead, H5N1 may stagger toward human transmissibility in steps. At some point it may be like SARS -- truly dangerous, spreading more easily from person to person, but not yet wildly contagious. It might still be stopped then.

Even if that proves impossible, the network still might save lives.

"Even if we can't stop it, the fact that we can say it has started may give countries weeks to go from planning right into operations," Ryan said.

In a full-blown outbreak, GOARN might end up as a "pandemic weatherman" -- Ryan's term -- telling the world where the virus is, how fast it is moving and where to expect it soon.