10/19/2026
October is Breast Cancer Awareness Month
Could persistent infections play a role in breast cancer? What does the research show? 🌿
Emerging research is investigating whether certain bacteria and viruses may contribute to breast cancer development or influence how cancer cells behave.
🔬 LYME DISEASE (Borrelia burgdorferi)
A 2024 study reported *B. burgdorferi* in breast cancer tissue, while laboratory studies published in 2021 and 2023 found effects on cancer-cell migration, invasion, and gene expression. These findings warrant further investigation, but do not establish that Lyme disease causes breast cancer.
🔬 BARTONELLA
Preliminary research has reported *Bartonella henselae* in samples from patients with inflammatory breast cancer. Other research has identified Bartonella-associated microbial signals in breast tumors. These findings are intriguing but limited, and a causal relationship has not been established.
What about other infections?
Researchers have also investigated Epstein–Barr virus (EBV), human papillomavirus (HPV), mouse mammary tumor virus–like sequences (MMTV), bovine leukemia virus (BLV), and cytomegalovirus (CMV). Some studies and meta-analyses report associations with breast cancer, but findings are inconsistent, and the role of these infections remains unresolved.
Why does this matter?Chronic infection, inflammation, immune dysregulation, and changes in cellular signaling are all biologically relevant areas of cancer research. Understanding whether specific infections contribute to cancer risk—or affect tumor behavior—could open important avenues for future investigation.
The next steps are independent replication, rigorous testing methods, and longitudinal studies establishing whether infection precedes cancer development.
Scientific curiosity matters. So does following the evidence. These findings do not prove that any of these infections causes breast cancer.
Sources:
- Borrelia burgdorferi in invasive breast cancer tissues (2024)
- Borrelia burgdorferi invasion of mammary epithelial cells (2021)
- Bartonella and inflammatory breast cancer (2012 conference abstract)
- The viral origins of breast cancer (2024 review)