John Barry, author of "The Great Influenza" and among the world's foremost historians on the influenza pandemic of 1918, is warning the world not to become complacent about the threat posed by the new swine flu virus.
A scholar at the Tulane-Xavier Center for Bioenvironmental Research in New Orleans, Barry describes the 1918 pandemic as the worst ever to befall humanity.
Although nobody has a reliable worldwide death toll, Barry says the lowest reasonable number is about 35 million and the real death toll could have been as high as 100 million people.
Now, with an outbreak of a new swine-flu virus spreading from human to human across the globe, Barry says the world should not be too complacent about the risk of another pandemic -- possibly coming in the autumn of 2009.
Second And Third Waves?
Barry notes that there have been four pandemics that historians and medical researchers now know about in great detail -- 1889, 1918, 1957, and 1968. He says all four had a first wave and a second wave "at least six months later and possibly as long as two years later." The 1889 and 1918 episodes, he adds, included third waves.
"It is possible that the second wave [of the 2009 flu virus], because the virus is more fully adapted to humans, could be more dangerous," Barry says. "In 1918, clearly the second wave -- that's the wave that people have heard about [and] that's what I wrote about -- that was the most deadly influenza pandemic we know about at any time in history. However, there is nothing in this [new] virus so far that looks like it is going to behave like 1918."
One big question about the new strain of flu virus is whether it will continue to be transmitted from human to human. If it does, it remains unclear how deadly the strain could become.
But Barry says he worries the new strain may seem to disappear during the summer -- but quietly continue to infect people around the world until it surfaces against in a stronger, mutated form.
He tells RFE/RL that governments and health workers may have just a few months to prepare for a wider outbreak.
"There is nothing that we can do to control what the virus does -- the virus is king, in one sense -- but there are still many things that we can do to prepare," Barry says. "The most important thing is to move vaccine production along -- it takes months to produce vaccine for a new virus. The other thing is the health-care infrastructure can be hardened. Preparations can be made, really, in a sort of anticipation."
Barry explains that a second-wave outbreak would be normal for a new virus.
"As far back as we can look in history, there were influenza pandemics. It's the nature of the virus that allows it to jump species -- its extraordinarily rapid mutation rate. And when it does that, it's not fully adapted. It's not very much at home," Barry says. "Therefore, it would not be at all unusual for it to be not as explosive as the usual influenza virus would be in that new environment while it is continuing to mutate -- continuing to make itself more at home."
Even if a fresh wave of the swine-flu virus spreads around the world later this year, Barry says he thinks it will be relatively mild compared to the 1918 pandemic.
"I certainly would not expect this virus to turn into anything like 1918, but I think it could turn into something like ordinary seasonal influenza," Barry says.
But he adds that that's not to say there's "nothing to worry about."
"Seasonal influenza, people are protected against -- whether they are vaccinated or not, their immune systems have seen that disease before and it gives them significant protection," Barry says, adding that such viruses mutate enough from year to year to evade the vaccine and immune systems, but individuals develop sufficient protection to escape the most tragic consequences.
But "this new virus is something nobody's immune system has ever seen before," Barry says, "so even if it is mild, it is going to affect so many more people if it becomes fully adapted that there will still be a significant death toll."
Barry notes that just because the current swine-flu outbreak has been mild outside of Mexico, that does not guarantee that it won't turn more deadly in the future.
He notes that the first wave of the 1918 influenza -- the outbreak during the spring of that year -- was extremely mild. It was in the fall of 1918 that a second wave of the outbreak spread much wider and turned virulent.
Indeed, Barry says a mutated strain of the swine-flu virus -- even one that is not as deadly as the 1918 influenza -- still could have a destabilizing effect on the world's economies.
He suspects it might be a "pretty mild second-wave virus" but says it might infect nearly one in three people in hard-hit areas.
"And that would create very significant economic impact because everywhere in the world, really -- everyone's supply chains, parts, and critical elements in the production process for almost everything come from some other country," Barry says. "If truck drivers are out sick, if air-traffic controllers are out sick so that air traffic is shut down, even power grids -- really, every aspect of society would be affected by 25 or 30 percent absenteeism. So even that mild virus would still cause tremendous disruption -- which I don't frankly think people have recognized yet."
Barry says fear and misunderstanding about the new swine-flu strain also can have a negative economic impact, such as when governments take inappropriate steps in a misguided attempt to prevent the spread of the disease. Chief among those is a decree last week by the Egyptian government that forced farmers to kill all 300,000 of the pigs in the country.
"There is no evidence that this virus, despite its name, actually entered the human population from swine -- and people look for that," Barry says. "Veterinarians monitor herds and pigs around the world are not sick. But it's already in the human population. At this point, to attack animals is just terribly wasteful and stupid."