Breast cancer, brain tumors not caused by viruses, study finds -- ScienceDaily

Breast cancer and brain tumors are not caused by viruses, according to a
recent genetic analysis of more than 4,000 tumors that maps the linkages
between viruses and 19 different types of cancer.

An estimated 1 in 5 cancers is caused by an infectious agent, either bacterial or viral. For years, scientists have traced the linkages piecemeal, scouring epidemiological data for clues about the agents behind specific cancers. In the new study, researchers screened the genomes of thousands of tumors at once to identify evidence of viral infection.

The study was not able to identify so-called "hit-and-run" viruses, which may have infected a person in the past but are no longer present in the tumor, or latent infections, in which a virus becomes dormant within a person's cells. New research addressing latently-infected tumors will be presented at Experimental Biology 2014.