In June 2025, two of our CLIC partners, Drs. Michael Scheurer and Joseph Wiemels joined a team of scientists at the International Agency for Research on Cancer (IARC) to discuss the evidence that showed hepatitis D virus (HDV), human cytomegalovirus (HCMV), and Merkel cell polyomavirus (MCPyV) cause cancer. The results of this evaluation are now published in the official IARC Monographs Volume 139 and in the Lancet Oncology Journal (citations below).
IARC Monographs on the Identification of Carcinogenic Hazards to Humans is the global authority on environmental factors that cause cancer in humans, and many national health agencies can use the IARC Monographs as a reference and scientific support for their research. At IARC, an interdisciplinary working group meets to classify various exposures into categories of risk to humans: Group 1 – carcinogenic to humans, Group 2A – probably carcinogenic to humans, Group 2B – possibly carcinogenic to humans, or Group 3 – not classifiable as to its carcinogenicity to humans.
The team with Drs. Scheurer and Wiemels evaluated three different viruses: hepatitis D virus (HDV), human cytomegalovirus (HCMV), and Merkel cell polyomavirus (MCPyV). HDV was classified as “carcinogenic to humans” (Group 1), MCPyV was classified as “carcinogenic to humans” (Group 1), and HCMV was classified as “possibly carcinogenic to humans” (Group 2B) based on “limited” evidence for cancer in humans.
Studies have shown that HDV is an RNA virus that causes hepatocellular carcinoma. HCMV can be transmitted via bodily fluids such as saliva, blood, urine, semen, and breast milk, and from mother to fetus during pregnancy, and causes lifelong infection. There is some data that shows HCMV causes acute lymphoblastic leukaemia (ALL) in children, but the evidence was limited, so this virus was categorized in Group 2B. MCPyV infections are typically acquired in early childhood via close contact between humans, and cause Merkel cell carcinoma.
These three viruses are closely related to our research on childhood cancers at CLIC. With the risk of transferring the virus from mother to child or contracting the virus while very young, these viruses have a real impact on the risk of childhood cancers. To date, CLIC studies have not specifically looked at the relationship between HCMV and childhood cancer, but we have investigated maternal infections during pregnancy. CLIC researchers are planning a publication on this subject in the near future.
For more information about the causes of childhood cancer visit our CLIC Research page: https://www.clic.ngo/research/
Citation:
Article Title: Carcinogenicity of hepatitis D virus, human cytomegalovirus, and Merkel cell polyomavirus.
Authors: Karagas MR, Kaldor J, Michaelis M, Muchengeti MM, Alfaiate D, Argirion I, Chen X, Cunha C, Hantz S, Koljonen V, Laude HC, Lui WO, Nevels MM, O’Brien TR, Scheurer ME, Touze A, Wiemels JL, Benbrahim-Tallaa L, de Conti A, Facchin C, Madia F, Pasqual E, Wedekind R, Aguilera-Buenosvinos I, Clifford G, Deng X, Dongoran RA, Ezzemni S, Huang Y, Suonio E, Zhai Y, Mattock H, Schubauer-Berigan MK, Kunzmann AT.
Published In: Lancet Oncol. 2025 Jun 26:S1470-2045(25)00403-6. doi: 10.1016/S1470-2045(25)00403-6. Epub ahead of print. PMID: 40587985.
IARC Monographs Link: https://www.iarc.who.int/news-events/iarc-monographs-evaluation-of-the-carcinogenicity-of-hepatitis-d-virus-human-cytomegalovirus-and-merkel-cell-polyomavirus/