BAKERSFIELD, Calif. -- The new H1N1 swine flu virus has infected at least 1 million Americans, according to the latest estimates from the Centers for Disease Control and Prevention.

Thankfully, most cases are mild. But reports on patients in Mexico confirm this new virus behaves more like a pandemic strain than a typical flu.

Doctors studying Mexican patients found that 87 percent of deaths were in younger people, between the ages of 5 and 59 years.

In contrast, just 17 percent of typical flu deaths are in this age group. Researchers concluded that if supplies of pandemic vaccine turn out to be limited, then priority should be given to younger generations.

A separate analysis noted that this new virus is a relative of an old foe -- the 1918 flu that killed millions worldwide. The genes of the 1918 virus have been mixing with other flu strains ever since, triggering periodic pandemics.

But there are signs that the pandemics are lessening in severity throughout the years, possibly because the genes have "learned" that they cannot survive if the virus kills its hosts.