Reference summary — not medical advice or a personal risk estimate.
Merkel cell polyomavirus (MCPyV)
Quick answer
Classified as Group 1 — carcinogenic to humans, based on sufficient evidence in humans. Infection. Common skin virus most adults carry without symptoms.
Summary
A common skin virus that causes a rare aggressive skin cancer.
Detail
MCPyV is Group 1 with sufficient evidence for Merkel cell carcinoma. Most adults are infected without symptoms; the cancer is rare and mainly occurs in elderly or immunosuppressed people.
What's not established
This classification is based on sufficient evidence in humans that this factor can cause cancer. It does not establish a safe exposure threshold, your personal risk, or how this factor's risk compares in size to other Group 1 agents — hazard classifications are not ranked by magnitude.
Regional relevance
global
Evidence sources
Every claim on this page traces back to one of these. Click through to read the primary document yourself.
Primary sources
NCI
NCI — Risk Factors: Infectious Agents
IARC
IARC Monographs — Classifications by Cancer Site, Vols 1–140
Supporting sources
ECDC
ECDC — Communicable diseases and cancer risk (European Centre for Disease Prevention and Control)
ACS
ACS — Known and Probable Human Carcinogens
NTP
NTP — Report on Carcinogens (US National Toxicology Program)
Last reviewed: October 2026
Official reference list
A government list some readers use alongside the primary evidence. Meyron is not affiliated with it. A chemical being listed does not by itself describe a risk from any particular product.
- California Prop 65 list
State of California's list of chemicals known to cause cancer or reproductive harm.