Bird flu has already killed millions of birds and dozens of people in Asia. But there is growing fear that the H5N1 virus could spark a human pandemic that would likely claim millions of human lives around the world.

Yet infectious diseases are unpredictable, and this presents a serious problem for risk communication. Health authorities know that if they sound the alarm too softly, it won’t be heard; it’s not easy to overcome people’s apathy and add another problem to their already long list of daily concerns. At the same time, too loud a warning can provoke excessive and premature fears, economic damage, and even an every-man-for-himself attitude that can result in chaos. And if no pandemic materializes, members of the public are less likely to take future warnings seriously.

A happy medium, say the authors, is to build mutual trust, “involving the public early, arousing an appropriate level of public fear, and helping people bear it.”

Sandman and Lanard provide a list of key recommendations to help authorities meet the risk communication challenges posed by bird flu and similar issues. Among their suggestions: engage in responsible speculation, acknowledge uncertainties about what will happen, share dilemmas about what to do, and do not try to eliminate fear altogether.

A special problem for risk communication about bird flu is that influenza is just not taken very seriously. It’s not exotic like SARS or West Nile virus. It happens every year, and it is usually a serious problem only for older adults. Moreover, the last severe pandemic was in 1918.

But a mutation or reassortment of the H5N1 virus could produce a strain that transmits easily between humans and thereby provoke a human pandemic that could, experts say, claim from 2 million to as many as 100 million lives or more (if, in a worst-case scenario, 30 percent of the population fell ill and 5 percent of those died).

The Perspectives in Health article appears as concerns about the pandemic threat are growing in the international public health community. At the recent World Health Assembly, Lee Jong-wook, Director-General of the World Health Organization, warned health ministers on what he called the “most serious known health threat the world is facing today, which is avian influenza.”

He said, “The timing cannot be predicted, but rapid international spread is certain once the susceptible virus appears. This is a grave danger for all people in all countries. We can get some idea of its magnitude from the Spanish influenza pandemic in 1918, which killed between 20 and 50 million people.”

Though scientists in 1918 “had very little idea of what was happening until it was too late,” Lee said, today, “by good fortune we have had time – and still have time – to prepare for the next global pandemic, because the conditions for it have appeared before the outbreak itself. We must do everything in our power to maximize that preparedness. When this event occurs, our response has got to be immediate, comprehensive and effective.”

Sandman and Lanard argue that motivating people to take the pandemic threat seriously should be a top priority for governments around the world. Authorities need to know how to involve the public in a positive way in preparations for a world crisis that almost certainly will happen…even if no one knows when.