Researchers have reported a link between the bovine leukemia virus and human breast cancer in a study published in PLOS ONE.

A team from the University of California, Berkeley, conducted a study (n=239) that compared breast tissue of women who had breast cancer and women who had no history of the disease for the presence of bovine leukemia virus (BLV). Of the breast cancer samples, 59% showed exposure to BLV as established by the presence of viral DNA and 29% of samples from women who had never had breast cancer indicated exposure to BLV. A statistical analysis showed that the likelihood of having breast cancer was 3.1 times greater if BLV were present than if BLV were absent.

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“Our results do not prove that the viruses cause cancer,” reported lead author Gertrude Buehring, professor of virology at UC Berkeley’s School of Public Health. She added that the team needs to confirm that the viral infection happened before, not after, the development of breast cancer. Findings from the study do not establish how the virus infected the breast tissue samples.

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