Exposure to the bovine leukemia virus from meat and dairy (or a blood transfusion from those who eat meat or dairy) is a risk factor for cancer. In 2015, researchers in California found bovine leukemia virus (BLV) stitched into the DNA of human breast cancer tumors from mastectomies. The virus was found at much higher rates than in normal breast tissue obtained from breast reduction surgeries. Based on this difference, they calculated that as many as 37% of breast cancer cases may be attributable to exposure to BLV, likely through consuming milk or meat from infected animals. In response, the...