Each year, 50 million Pap tests are performed in the USA to screen women for cervical cancer. In the more than half a century since physician George Papanicolaou developed the test, the U.S. death rate from cervical cancer has dropped 70%.

Caught early, cervical cancer has a five-year survival rate of 95%. But it still kills nearly 5,000 U.S. women every year, and it's the second-leading cancer killer of women worldwide. In some cases, Pap tests missed cancers or the cellular changes that preceded them. In other cases, cervical cancer patients never got Pap tests.

Scientists appear to be homing in on an alternative to Pap tests: testing for a cancer-causing virus (story, 1A). Over the past 15 years, a growing body of research has pointed to human papillomavirus, or HPV, as a major cause of cervical cancer.