One of the most worrisome things about the swine (H1N1) flu when it first emerged almost three weeks ago was that it seemed to hit young, healthy people disproportionately hard. That raised the specter of the 1918 Spanish flu, which was so fearsome in part because it was deadliest among people ages 20 to 40.

But as the disease spreads around the country and the world (now to 43 states plus the District of Columbia and 30 countries) it appears that the swine flu, like the more familiar seasonal flu, tends to prey on the weakest. The two deaths over the weekend, for example, were reported to be people who had underlying chronic diseases—a man from Washington State with heart disease, and another in Costa Rica with diabetes and chronic lung disease. Similarly, most people who develop serious complications from the seasonal flu each year have a chronic disease or are over age 65. "That's why experts recommend that they, in particular, should get an annual flu shot," says John Santa, M.D., M.P.H, director of the Consumer Reports Health Ratings Center.