One in eight of the cancer cases worldwide in 2024 are believed to have been caused by infections, a new study by the International Agency for Research on Cancer (IARC) found. This equates to 2.3 million (or 12 percent) of the new cancer cases that year, with five infections causing a considerable proportion of those cases. The researchers at the IARC therefore said that the findings suggest a "significant proportion of the global cancer burden is preventable through better infection control." The study was published in the journal Lancet Oncology on September 28.
"This fraction, one in eight cancer patients, is the same fraction as lung cancer in all cancers in the U.S. It is not a rare or insignificant problem," Dr. Patrick Moore, chair in Innovative Cancer Research at the University of Pittsburgh, told Newsweek, adding that the IARC's estimates may also be "very conservative," meaning the "actual fraction of cancers caused by infection is likely to be still larger." He said infection is a "much more important factor in cancer than most people recognize and the importance of each specific infection is highly related to geography." He added that cut-backs in HIV treatment due to the disbanding of USAID "will lead to increased infectious cancers in sub-Saharan Africa, while in Asia, expansion of neonatal HBV vaccination may dramatically reduce liver cancers caused by this virus." Karl Munger, a professor of developmental, molecular and chemical biology at Tufts University, told Newsweek that the IARC's estimate is "lower than I would have expected.
Other analyses have suggested that infection-associated cancers account for 15 to 20 percent of cancer cases globally, although the proportion is considerably lower in the U.S. and other high-income countries." He added that the finding is "significant because infections are a frequently overlooked and underappreciated cause of cancer. Importantly, many infection-associated cancers are preventable." Based on the findings of the study, the leading infectious causes of cancer in 2024 were Helicobacter pylori (or H. pylori), human papillomavirus (HPV), hepatitis B virus (HBV), Epstein–Barr virus (EBV), and hepatitis C virus (HCV). H. pylori was linked to the highest number of cases—at around 760,000 cancer cases globally that year.
These cases were mainly gastric (stomach) cancer. HPV was linked to about 750,000 cancer cases globally, which were predominantly cervical cancer, as well as anal, vulvar, vaginal, and penile cancers and some head and neck cancers. HBV was linked to about 360,000 cancer cases in 2024, and most were cases of liver cancer.
EBV was linked to about 260,000 cancer cases globally that year, which were largely nasopharyngeal cancer, some gastric cancers, and Hodgkin lymphoma. HCV was linked to about 160,000 cancer cases and most were cases of liver cancer. The researchers also found that the burden of cancer cases was highest in Eastern Asia, Sub-Saharan Africa, Central and Eastern Europe, and South-East Asia.
Specifically, Eastern Asia had a particularly high burden from H. pylori and HBV, whereas Sub-Saharan Africa had very high rates of HPV-related cancers and a substantial burden from infections with HIV and Kaposi sarcoma-associated herpesvirus (KSHV). They said that the regional differences likely reflect "variations in the prevalence of infections, access to prevention and treatment, and broader social and economic conditions." Dr. Shan-Lu Liu, co-director of the Viruses and Emerging Pathogens Program at The Ohio State University, told Newsweek that he found the findings "both striking and encouraging." "The encouraging part is that many of these cancers are potentially preventable through vaccination, infection control, screening, and treatment," he said.
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