The World Health Organization says Severe Acute Respiratory Syndrome is only the first of what experts expect will be many emerging infectious diseases this century. The WHO says it is particularly concerned about future pandemics of influenza.
The head of WHO's communicable diseases program, David Heymann, says the World Health Organization has no doubt that more previously unknown, life-threatening infectious diseases will hit the world sooner or later. He says the big concern is influenza.
"And that was the concern at the start of this outbreak, when we saw an unknown respiratory disease, which was spreading to health workers and which was of unknown cause. One of the concerns was that it was influenza," he said. " There will be more outbreaks like SARS. There will be more outbreaks that spread internationally. Influenza, we are almost certain, will occur in a global pandemic form, as it did three times in the last century. And many other diseases, which we do not even know, such as AIDS 20 years ago, may come, and may become other endemic diseases in human populations, remaining with us from now on forward."
Dr. Heymann says that, unlike SARS, influenza is an airborne disease that spreads rapidly and is highly lethal. One influenza pandemic early in the 20th century killed an estimated 20 million people.
SARS, on the other hand, spreads mainly through close contact from one infected person to another, and although it, too, can be lethal, 85 percent of its victims recover.
WHO virologist Karl Stohr says the world must do more to prepare for an influenza outbreak. He says that, first and foremost, government health systems must strengthen surveillance of infectious diseases.
"We need to understand very quickly when a new disease is happening. We should be able to detect it and to respond to it very quickly," he said. "Strengthening surveillance also includes laboratory surveillance. The second area which is specific for influenza is that, very quickly, vaccines and other drugs should be developed, and that will take at least six months, irrespective of the strain, which is going to develop. And the third area is that countries should strengthen their national pandemic preparedness, to be able to control efficiently health, or to contain and to deal with a health emergency of a pandemic influenza."
Mr. Stohr says that between 10 and 15 percent of the total population is likely to become infected with influenza. He says many national health systems are likely to become overburdened, as they attempt to grapple with large numbers of severely ill people and many deaths.