Some infections can exact a lingering toll on our body, long after their initial bout of illness. Research out this week shows that infectious diseases contribute to millions of new cancer cases every year.
Researchers with the World Health Organization examined the cancer-related burden of a dozen different infectious diseases, including human papillomavirus (HPV) and HIV. Collectively, they calculated, these diseases helped cause roughly one out of every eight cancer cases in 2024. Many of these infections are preventable and/or treatable, highlighting the value of effective screening and infection control programs, the researchers say.
A cancerous burden
Scientists have long known that certain infectious diseases can raise the risk of cancer. Several types of HPV, for instance, are responsible for the vast majority of cervical cancer cases, though it also strongly contributes to several other kinds of cancer found in both women and men.
The International Agency for Research on Cancer, the specialized cancer division of WHO, has included 13 infectious pathogens in its list of Group 1 carcinogens, the category used for things that have the strongest evidence supporting their ability to cause cancer. And the IARC has periodically tried to quantify how much cancer these diseases inflict, with the last tally taking place in 2018. This latest update is the most comprehensive yet, according to the authors, and incorporates more recent research on the carcinogenicity of infections like HIV and Merkel cell polyomavirus (MCV).
This time around, the researchers analyzed the burden of 12 infections: the viruses HPV, HIV, hepatitis B and C, Epstein-Barr virus, Kaposi’s sarcoma-associated herpesvirus, also known as human herpesvirus 8, human T-cell lymphotropic virus type 1 (HTLV-1), and MCV; the bacterium Helicobacter pylori, notorious for causing stomach ulcers; and three parasitic fluke worms, Opisthorchis viverrini, Clonorchis sinensis, and Schistosoma haematobium. The only Group 1 pathogen not included in the analysis is hepatitis D, a strange satellite virus that can only infect people who already have an existing hepatitis B infection.
Ultimately, the researchers found, these diseases contributed to 2.3 million cancers in 2024, or roughly 12% of all cases that year. The single largest burdens came from H. pylori, which caused about 760,000 cases of mostly stomach cancer, and HPV, which caused about 750,000 cancer cases, mostly cervical. Hepatitis B also caused more than 300,000 cancers, and hepatitis C over 100,000 cases, both of which were mostly liver cancer. The team’s findings were published Tuesday in The Lancet Oncology.
The role of prevention and treatment
Some of these infections, like Epstein-Barr virus, are essentially unavoidable for the time being. Yet many others are preventable or treatable.
There’s now a highly effective vaccine for HPV that can prevent the most prevalent cancer-causing types as well as a vaccine for hepatitis B, for instance, while chronic H. pylori infections can be treated with antibiotics and chronic hepatitis C is now nearly 100% curable with the latest antivirals. Pre-exposure prophylaxis for HIV is also highly effective at preventing infection for people at higher risk of exposure, and prompt treatment of HIV can make it virtually impossible for people to transmit the virus to others. And all three parasites can be treated with antiparasitic drugs or prevented via improved sanitation and food safety (these infections are usually caught through eating raw/undercooked freshwater fish or drinking tainted freshwater).
In other words, many of these cancer cases likely never have to happen.
“The findings underscore the major role that infection control can play in reducing the global cancer burden,” said study co-author Harriet Rumgay, a scientist in the Cancer Surveillance Branch at IARC, in a statement from the IARC.
Unfortunately, controlling these infections is a task easier said than done, even in well-off countries like the United States. Though the HPV vaccine is widely recommended for everyone starting as early as age nine, vaccination rates are lower in the U.S. than many similar high-income countries. And as of 2024, only about 63% of U.S. teens were up-to-date with their HPV shots, whereas countries like Denmark and Spain are expected to reach 90% coverage by decade’s end. The hepatitis B vaccination rate is also in danger of falling here, thanks to an ongoing effort by antivaccination advocate and current health secretary Robert F. Kennedy to strike down the federal government’s recommendation for at-birth vaccination.
Troubling as things are stateside, however, the researchers note that the burden of infection-related cancers is still greater in low- and middle-income countries.
