Nearly 2 million Americans could die in a flu pandemic, which many scientists say is not just inevitable but long overdue. In such an emergency, national leaders would need to be forthright and candid to gain our trust — or risk chaos.

But recent polls show that President Bush's approval ratings have sunk below 50 percent and that deception about the Iraq war, as well as federal mismanagement after Hurricane Katrina, have hurt his credibility. That loss of public faith is almost as scary as the virus itself. When citizens are skeptical or defiant in the face of severe disease, fear becomes epidemic, leading to confusion and often needless deaths.

"One of the hardest things — and one of the most crucial things — about preparing for a public health crisis is cooperation from the public and trust in government," said Judith Walzer Leavitt, professor of medical history at the University of Wisconsin. Leavitt's study of two smallpox outbreaks — Milwaukee's in 1894 and New York City's in 1947 — illustrates how important this trust may be if a deadly new strain of influenza sweeps the world.

When smallpox struck Milwaukee, health officials permitted middle- and upper-class residents to be quarantined at home but ordered residents in the city's crowded immigrant sections to an isolation hospital known as the "pesthouse." Angry at the injustice, immigrant groups hid smallpox victims from authorities. The health commissioner told a newspaper reporter: "I am here to enforce the laws, and I shall enforce them, if I have to break heads to do it." Riots broke out, and smallpox raced through the city. By the end of the outbreak, 1,079 Milwaukeeans were infected and 244 died.

Compare this with New York City's enlightened smallpox communication in 1947. After three cases had emerged, the health commissioner said that while the chances of a full-scale epidemic were slight, everyone who had not been vaccinated should "go at once to their doctors to receive this protection." Officials held daily news conferences, announcing all suspected and confirmed cases. People felt they were being informed as events unfolded. Within four weeks, an astounding 6,350,000 residents were vaccinated. The virus caused only 12 cases and two deaths.

Words count. "The core of crisis communication is demonstrating competence, transparency, passion and compassion," said Howard Koh, director of the Center for Public Health Preparedness at the Harvard School of Public Health and a former Massachusetts commissioner of public health. Against those standards, if a flu pandemic hit tomorrow, this White House's words would fall on deaf ears.

How can leaders launch a vital national conversation on pandemic influenza?

First, they must earn back Americans' trust. That has been squandered in the failed federal response to Hurricane Katrina, the daily horror in Iraq, the unsolved epidemic of mail-borne anthrax in 2001 and the color-coded terror alerts after 9/11. Even the president's flu plan, announced in early November, seemed tardy.

The president and other officials should concede these earlier failures, said Peter Sandman, a risk consultant based in Princeton, N.J. Here's the pitch that Sandman suggested health officials give: "Look, it's hard for us to be the ones to warn you. Some of you are thinking about Iraq, where we warned you and we were wrong. Some of you are thinking about Katrina, where we were warned and we didn't respond well. Lots of you are thinking about the fact that if we're going to take this issue seriously now, why weren't we taking it seriously two years ago and gearing up properly? We come to this with a very imperfect record — but we've got to tell you about it anyhow."

Second, the Bush team must straightforwardly warn Americans about how bad a novel strain of flu could be. The president's statement at an October news conference — "rest assured that we're doing everything we can" — was patronizingly dishonest.

Skilled risk communication is frank, said Monica Schoch-Spana, a medical anthropologist and senior fellow at the Center for Biosecurity at the University of Pittsburgh Medical Center. "It's resetting a baseline expectation: that people get sick and can die from flu, and in extraordinary outbreaks that can happen at a large scale."

In crises, great communicators help citizens steel themselves for suffering, while also protecting them. "But we first have to admit that something tragic will happen," Schoch-Spana said.

Most important, leaders must take real action to get the country ready. Until now, the Bush administration has largely ignored this long-feared catastrophe. It forced local public health departments to divert their scarce resources to bureaucracy-laden bioterrorism preparedness. It didn't offer ways for hospitals to handle a flood of patients should disaster strike. It dismissed the need for domestic vaccine production. It failed to order enough Tamiflu — and by the time it tried, many other governments were standing ahead of us in line.

The Pandemic Influenza Plan leaves cash-strapped and staff-starved state and local health departments to pay for drugs and other vital necessities and to logistically handle a crisis on their own. That approach makes sense in one respect, because all public health preparedness and response ultimately takes place locally.

But in a global economy, no locality could be wholly self-sufficient for the 12 to 18 months that a pandemic would play out. "There are a lot of things besides vaccines and antivirals that are going to be critical," said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. "At this point, we virtually have no plans for that: masks, syringes, needles, IV bags, ventilators, food supply."

We don't know where we'll get the medicines we take daily, the fuel that keeps us warm and runs our transportation, the consumer products and services we rely on. "This will have all the makings of a slow-motion worldwide tsunami," Osterholm said. "You never can be fully prepared for this. But there are many things we can do."

To truly earn the public's trust, national officials should issue regular progress reports on the nuts and bolts of protecting us (and the rest of the world) against a lethal flu virus. The issue should be kept front and center, just as our leaders manage to keep the terrorism threat front and center. As a bonus, officials might draw up national plans to revive the long-neglected public health system and guarantee healthcare for all Americans, even in non-pandemic times.

But until words are paired with such actions, the administration's spiffy new campaign to warn us about pandemic flu amounts to little more than spin.

Madeline Drexler is a Boston-based journalist and author of "Secret Agents: The Menace of Emerging Infections."