For years health authorities have warned of the growing threat posed by drug-resistant bacteria, but most of us have been half-listening. Not anymore.

A virulent strain of bacteria that resists many antibiotics appears to be killing more people annually than AIDS, emphysema or homicide, taking an estimated 19,000 lives in 2005, according toa study published last week in The Journal of the American Medical Association. The recent death of a 17-year-old high school football payer in Virginia is a tragic reminder that methicillin-resistant Staphylococcus aureus, or MRSA, can prey on otherwise healthy people.