Cattle virus linked to breast cancer: Evidence of exposure to bovine leukemia virus was found in breast cancer cells, however researchers said that does not prove it causes cancer.
Researchers were surprised to find in a new study that a significant number of breast cancer cells from more than 200 women had evidence of exposure to bovine leukemia virus, or BLV.
BLV infects dairy and beef cattle's blood cells and mammary tissues, and was for a long time thought not to be able to infect humans.
Nearly all bulk milk tanks at large factory farms are infected with BLV, but only about 5 percent of cows get sick if they have the virus, according to the U.S. Department of Agriculture. The same group of researchers at the University of California Berkeley involved in the new study also found last year that BLV could be transmitted to humans.