Infections Linked to 1 in 8 Cancer Cases Worldwide, Major Study Finds

Infections are linked to approximately one in eight new cancer cases globally, totaling 2.3 million cases in 2024, according to a significant analysis by the International Agency for Research on Cancer (IARC).

The study identified 12 specific infections contributing to human cancer diagnoses. Among these, Helicobacter pylori (H. pylori), human papillomavirus (HPV), hepatitis B virus (HBV), Epstein-Barr virus (EBV), and hepatitis C virus (HCV) were identified as the primary drivers, accounting for the majority of infection-related cancer cases.

"The findings underscore the major role that infection control can play in reducing the global cancer burden," said Dr. Harriet Rumgay, a scientist at IARC and co-author of the study, in a press release. "Despite progress in vaccination and screening, infection-related cancers remain a major global challenge, with the burden falling disproportionately on populations in low- and middle-income countries."

Many of the identified cancers could potentially be prevented through vaccination, treatment, or screening measures, according to the researchers. The findings were published in The Lancet Oncology on September 28.

While infections are a significant factor, experts emphasize that most cancers are not caused by infections. "Most cancers are not caused by infection," stated Dr. Joshua Cohen, medical director of the Gynecologic Cancer Program at City of Hope Orange County, who was not involved in the study.

HPV is a notable cause of cancers affecting the rectum, vagina, cervix, and oropharynx. "Eighty percent of the population has been exposed to certain types of HPV strains," Dr. Cohen explained. "About 40,000 people in the U.S. are diagnosed with these cancers each year." For most individuals exposed to HPV, the immune system clears the virus, though the reasons for varied immune responses are not fully understood.

Gastric cancer, less common in the U.S. but prevalent globally, is linked to H. pylori, a stomach infection. While H. pylori screening is not routine in the U.S., individuals experiencing symptoms like peptic ulcer disease or significant stomach pain are advised to consult a gastroenterologist.

Preventive strategies are available to mitigate the risk of infection-related cancers. "As a patient, the most important thing is to think about your health, what you can do to prevent yourself from developing these infections or your family," Dr. Cohen advised. He highlighted the availability of HPV vaccination, particularly for individuals under 45 who have not been vaccinated, as a means to prevent many associated cancers.

Experts caution that contracting one of these infections does not guarantee cancer development. "The vast majority of patients who have an HPV infection or H. pylori, or even hepatitis B or C, are not going to develop cancer," Dr. Cohen noted. However, he stressed the importance of seeking treatment for these infections due to their established links with certain cancers.

Patients experiencing symptoms such as persistent epigastric pain, acid reflux, abnormal vaginal bleeding, or difficulty swallowing are encouraged to seek medical attention, as these could be indicators of conditions related to infections or cancer. "There are steps we can take as doctors to keep you safe and hopefully reduce the risk of developing cancer for those that have had an infection," Dr. Cohen added.