This is not 1918

The swine flu outbreak in Mexico is disturbing, and fears of a pandemic are justified. But the best advice on Monday came from President Barack Obama. "This is obviously the cause for concern and requires a heightened state of alert," Obama noted. "But it's not a cause for alarm."

As of Monday afternoon, swine flu was believed to have killed 149 people in Mexico and sickened more than 1,600.

There have been at least 40 cases in the United States, including 28 at a high school in New York City.

The outbreak in Mexico recalled the horrific worldwide pandemic that killed 50 million at the close of World War I and sickened millions more. But this is not 1918. In the 91 years since those terrible days, the understanding of infectious diseases has grown far more sophisticated.

This is a serious situation and alarming because so little is known, including whether the virus is mutating into a more lethal form. But state and the local health departments appear to be well prepared if an outbreak occurs.