Oncogenic viruses: Approximately what proportion of human tumours worldwide are associated with a viral risk factor?

Introduction / Context:
Cancer etiology includes infectious causes. Several human viruses are classified as oncogenic or cancer-associated, contributing to a significant fraction of global cancer burden through chronic infection, inflammation, and direct oncogene expression.

Given Data / Assumptions:

• High-burden viruses include HPV, HBV, HCV, EBV, HTLV-1, KSHV, and Merkel cell polyomavirus.
• Global estimates aggregate across regions with varied prevalence (e.g., higher HBV/HCV in some areas).
• We are asked for a broad, widely cited upper-bound estimate.

Concept / Approach:
Epidemiological studies estimate that approximately 15–20% of human cancers have an infectious (often viral) component, with variation by geography and income level. This figure captures cancers such as cervical (HPV), hepatocellular carcinoma (HBV/HCV), certain lymphomas and nasopharyngeal carcinoma (EBV), adult T-cell leukemia/lymphoma (HTLV-1), Kaposi sarcoma (KSHV), and Merkel cell carcinoma (MCV).

Step-by-Step Solution:

Verification / Alternative check:
International cancer agencies (e.g., IARC) and global burden studies regularly cite ~15–20% worldwide, higher in certain regions.

Why Other Options Are Wrong:

• Up to 10%: underestimates the aggregate burden.
• Up to 30% or 40%: exceed commonly accepted global estimates.

Common Pitfalls:
Confusing regional peaks (where infection-related cancers are more prevalent) with the global average.

Final Answer:
Up to 20% of human tumours have a viral risk factor