Author John M. Barry thinks we're overdue for a plague. Barry, who spent seven years researching the 1918-1919 influenza pandemic for his latest book, said the coming outbreak will take a familiar form: flu.

Since the publication of The Great Influenza: The Epic Story of the Deadliest Plague in History by Viking Press last February, the author has lectured widely, addressing the world's top infectious-disease experts about modern bird flu. He tells them H5N1 could prove far deadlier than even the 1918-1919 influenza virus, which killed up to 100 million people worldwide.

Now on book tour, Barry recently corresponded with the Post's Elena Lesley, giving his take on flu-past and present-and stopping a Cambodian epidemic.

Post: What was the inspiration for your latest book, The Great Influenza: The Epic Story of the Deadliest Plague in History? Did you begin researching this book with the 1997 Hong Kong bird flu outbreak in mind?

Barry: No. I actually started the book prior to the outbreak. What interested me was both how the larger society and, within it, the scientific community, responded to the almost unimaginable crisis in 1918 and 1919 - according to Nobel laureate and Australian medical scientist McFarlane Burnett, between 50 and 100 million dead, in a world with a population only 28 percent as large as today's.

Post: Are there estimates of the toll the 1919-1918 outbreak had on Asia, specifically Southeast Asia? Did European and American health systems help mitigate the effect s of the outbreak in a way that might not happen in less developed countries like Cambodia?

Barry: As you can tell from the range of the estimates even from a Nobel laureate who spent most of his life studying the disease, no one really knows how many died, especially in the part of the world where there were then unreliable vital statistics. But in Southeast Asia it was certainly in the millions. As far as medical practice goes, in 1918 of course medicine could do little except keep people hydrated.

The most important lesson for an area like Cambodia is for the government to tell the truth about the risk, and not give false reassurance. All that does is lead eventually and inevitably to a breakdown in the trust in authority. If there is a new pandemic, there will be fear. That's impossible to prevent. But trust in authority alleviates panic. Also people need to be organized in order to provide even the most basic care. In 1918 people died of starvation or dehydration because they got no care at all, and there was no one to help them.

Post: Can you compare the potential origins and transmission of the 1918 virus with modern-day bird flu strains?

Barry: It's the same. All influenza viruses - all of them - come initially from birds. The virus mutates rapidly, which gives it the ability to jump species to people. Not all pandemics are as lethal as 1918, not to mention H5N1. Pandemics in 1957 and 1968 were serious, killing two to eight million people worldwide, but were nothing like 1918 or the threat of H5N1. The 1918 virus probably jumped from birds to people in the United States. But most - not all, but most - pandemics throughout history (three to five per century over the last five centuries) have started in Asia.

Post: How does current bird flu compare (in terms of severity of symptoms, death rate) to previous strains of influenza?

Barry: H5N1 generates symptoms similar to 1918, but has a much higher case fatality at this point. If we are so unfortunate as to see that virus become transmissible easily from person to person, we can only pray it becomes less lethal. No known influenza virus in history, including 1918, has anything like the mortality rate of H5N1.

Post: Do you think the shortage of US flu vaccines this fall brought more visibility to the avian influenza virus, even though they weren't specifically manufactured for bird flu?

Barry: The debacle in the United States has definitely gotten attention from the US government. Even though Bush's overall budget is down for domestic spending, and for many public health agencies, the administration raised its spending significantly on flu, and it's up tenfold since 2001. The request is for $439 million for next year.

Post: How likely is the development of a new strain of the virus that can be easily transmitted among humans? How would humans spread this new strain? Coughing? Sneezing? Doorknobs? What kinds of areas would be most at risk for epidemic?

Barry: The National Academy of Sciences in the United States says another pandemic is "not only inevitable, but overdue." It will come. A virus can jump to people anywhere. In Holland in 2003 a virus infected 89 people and killed one. But most vulnerable is Asia, because that's where large numbers of people are in direct contact with birds.

Once the virus does mutate into a form that passes from person to person, it can either be spread by coughing, or by contact between a hand and a hard surface like a doorknob, when your hand then goes to your mouth or nose.

Post: Why is the world "overdue" for a pandemic?

Barry: There have been three to five a century for at least 500 years. The last one was 1968. There are at least three viruses right now threatening to jump to humans. H5N1 is only the most dangerous of them.

Post: In your opinion, what are the best methods for controlling firstly, a flu outbreak, and secondly, a human pandemic?

Barry: Massive investments in vaccine infrastructure, stringent public health controls including strict quarantines, stockpiles of antiviral drugs (especially oseltamivir) and absolute truth-telling from governments.

Post: Family members of Cambodia's first confirmed bird flu victim (a farmer who lived near the border with Vietnam) claim they had never even heard of the virus. What are your concerns regarding transmission in a country like Cambodia, where large numbers of citizens are poor and uninformed and there is little governmental infrastructure?

Barry: You have just described a very dangerous situation, and Cambodia is not alone. Much of Africa is in the same situation. All the poorer countries are in the same situation.

Post: If bird flu mutates into a strain easily transmitted among humans, do you think the virus will lose its "bird" label, becoming just another influenza outbreak?

Barry: The label doesn't matter. As I said, all flu viruses originally came from birds. The only thing that matters is how virulent the virus is, how easily it spreads, and how prepared and aggressive we are in combating it.