Who Dies When the World Catches the Flu?

The chances of something happening on the other side of the world directly affecting us here are pretty slim.

With globalization, though, this is changing. What happens in East Asia today may very well have a huge impact on us tomorrow. And it may even kill us.

These days, diseases such as the flu can travel globally in a very short period of time. And now researchers at the Harvard Initiative for Global Health at Harvard University predict that as many as 81 million people in the world could die in one year if a very contagious form of the flu spread in modern times.

Just to put that number in perspective, the total number of human deaths from all causes last year was 58 million.

Pandemics -- global disease outbreaks caused by viruses or other organisms -- usually occur because the type of organism is new. Our immune system has trouble fighting it, as it has never seen it before.

The study is published in the current issue of the British medical journal Lancet.

"We wanted to see what the actual numbers might look like," said Dr. Christopher Murray, professor of public policy and social medicine and director of the Harvard Initiative for Global Health.

To do this, the researchers applied historical death to current populations to see what would have happened if a virus spread around the globe in 2004. They expected a death toll between 15 million and 20 million.

What they found out was that between 51 million and 81 million individuals would die in current times if a pandemic like the 1918-20 flu hit -- and 96 percent of these deaths would be in developing countries.

'Pandemics Are Just Like Earthquakes'

With the avian influenza epidemic in birds and the few hundred cases recorded in humans, some fear that a bird flu pandemic is approaching. However, the onset of such an event is difficult to predict.

"Flu pandemics are just like earthquakes," said Kenneth Hill, associate director of the Harvard Center for Population and Development Studies at Harvard University and co-author of the study. "Major outbreaks are by no means regular. And you can't predict that the next one will be this year or the next.

"All you can say is that based on historical records and probabilities, a major one is likely to happen," Hill said.

Experts say that, on average, flu pandemics happen every 30 to 40 years, and it is not possible to say how serious a new pandemic will be. It depends on the characteristics of the new virus.

The 20th century saw three main pandemics -- in 1918, 1957 and 1968. The 1957 and 1968 pandemics each killed 1 million to 2 million people -- a relative drop in the bucket. The one in 1918 killed more than 20 million and is often used as a theoretical upper limit for future pandemics.

"Since it is hard to say if future ones will be more like a 1918 or a 1957 pandemic, it certainly makes sense to be prudent and do what we can to prepare ourselves for a pandemic," Murray said.

What Preparation Means

"Unfortunately, we can't avoid pandemics," Murray said. "But we can reduce the number of cases that occur and reduce the number of deaths."

One interesting result of the study was that it showed a large variation in how different countries around the world would be affected by the pandemic. And poorer countries would likely bear the brunt of the catastrophe.

"[In 1918], the poorer the country, the higher the mortality from the flu," Murray said. There was more than a 30-fold variation in mortality between countries they noted.

The researchers say the situation would be the same today.

This highlights the fact that despite medical advances, the disparities in health between rich and poor countries continues to remain extremely high, experts said. The poor continue to not benefit much from the increased wealth and advancements that the rest of the world is seeing.

"There are two main reasons why the poorer countries have a greater proportion of the deaths," Hill said. "One is that the health infrastructure is weaker in developing countries. And the second is that the populations are less healthy to begin with."

"Due to poor nutrition and other diseases the poor are more easily compromised."

Other experts agree that given the conditions in which many in the developing countries live -- where there is overcrowding and limited or no access to simple things like clean drinking water -- it is not surprising to see such a stark contrast.

U.S. Would Not Be Safe

While the United States has a detailed pandemic preparedness plan, the researchers say it will not be able to avoid a pandemic if one were to occur.

"We have the ability to monitor new strains of influenza and create vaccines, which may be of help, but we cannot completely protect ourselves in that way," Hill said. "The thing about influenza virus is that it is extremely contagious. It is hard to control if it gets into the human population."

"The 1918 influenza spread around in a matter of weeks even without air traffic. Attempts to seal off borders don't work," Hill said.

While the 1918 pandemic is a worst-case scenario, there is no guarantee that the next pandemic will not be even more deadly. And experts agree that one of the best ways to prevent the deaths from such a virus would be to make sure that developing countries are better prepared to handle a pandemic.

"Developed countries have an obligation to protect the population of developing countries," Hill said.

"In many ways there hasn't been enough focus on helping poor countries to have practical strategies to prepare for the flu," Murray said. "Because most of the mortality will be in poor countries, we need to focus more policy attention in helping them in coming up with effective strategies."

"It's a moral imperative alone," Murray said.