Two new studies presented this week at the European Lung Cancer Conference in Geneva have linked the human papillomavirus (HPV) and the measles virus to the risk of lung cancer. Both studies focused on the viral impact on non-small cell lung cancer. About 85 to 90 percent of all lung cancers are of this variety.

In the first study, scientists from the University of Louisville in Kentucky looked at lung cancer tissue samples from 23 patients, all of whom were smokers. Five out of 22 non-small cell lung cancer samples were HPV-positive. Researchers believe HPV may act as a co-carcinogen by increasing the risk of cancer among those who smoke and that a vaccine may someday be able to help protect people from the disease. HPV is already known to be the cause of cervical cancer and a potential cause of head and neck cancers.

The second study, conducted in Israel, included tissue samples from 65 patients with non-small cell lung cancer. Researchers found that more than half of the samples tested positive for the measles virus. The scientists believe that the measles virus modifies the effect of other carcinogens and does not cause cancer by itself.

Experts caution that more research needs to be done on each front before definite viral links to lung cancer can be proven.