New global data is putting a sharper spotlight on a group of infections that can quietly feed into cancer risk, with researchers tying about one in eight new cases worldwide to infectious causes. The biggest names on the list are familiar ones, including H. pylori, HPV, hepatitis B, and hepatitis C, and the message from doctors is simple: prevention, screening, and treatment still matter a lot.
In 2024, that translated into an estimated 2.3 million cancer cases linked to infection, according to a new analysis from the International Agency for Research on Cancer. The study identified 12 infections connected to human cancers, ranging from common viruses to a few parasites and bacteria that most people have heard of but do not always think about in a cancer context.
The five biggest contributors did most of the heavy lifting. H. pylori was tied to about 760,000 cases, HPV to roughly 750,000, HBV to around 360,000, EBV to about 260,000, and HCV to close to 160,000.
Those numbers are striking, but they do not mean infection automatically leads to cancer. Dr. Joshua Cohen, a gynecologic oncologist at City of Hope Orange County in Irvine, said most cancers are not caused by infection, even though some infections clearly raise the odds over time.
The study’s authors also stressed that infection control can make a real dent in the global cancer burden. Dr. Harriet Rumgay, a scientist in the Cancer Surveillance Branch at IARC, said vaccination, screening, and treatment have already helped, but infection-related cancers still hit low- and middle-income countries especially hard.
That’s where the public health angle gets serious. In places with weaker access to vaccines, tests, and follow-up care, infections can linger longer and do more damage, which gives them more time to trigger the chain of events that can eventually lead to cancer.
The analysis looked at cancer data from 2024 and was published in The Lancet Oncology on Sept. 28. It also came with a few important limits, since the researchers used population-level estimates instead of tracking individual patients over time.
That means the results depend on how strong each country’s cancer data is, and the real impact may even be bigger than the estimate suggests. The study only counted infections already proven to cause cancer, so it likely leaves out some of the broader picture.
HPV stands out as one of the most important examples because it is tied to cancers of the cervix, vagina, anus, rectum, and the back of the throat. Cohen said about 80% of people are exposed to certain HPV strains at some point, yet the body clears the virus in most cases.
Still, HPV is behind a large share of cancers that doctors see every year. Cohen said about 40,000 people in the U.S. are diagnosed with these HPV-related cancers annually, which is a big reason vaccination remains such a powerful tool.
H. pylori tells a different story. The bacterium lives in the stomach and is linked to gastric cancer, though Cohen noted it is more common in other parts of the world than in the U.S.
People with peptic ulcer disease or significant upper abdominal pain should talk with a gastroenterologist about testing and treatment, he said. The idea is not to panic, but to catch the problem before it has time to keep causing damage.
That same practical approach applies to hepatitis B and hepatitis C, both of which can drive cancer risk if infections are not addressed. Even when an infection does not lead to cancer, it can still create the kind of long-term inflammation and tissue injury that raises concern.
For prevention, Cohen pointed to one major advantage Americans have: access to the HPV vaccine. He said people under 45 who have not been vaccinated should look into it, since it can reduce the risk of several HPV-linked cancers.
Doctors also lean on screening and early treatment when infections are already present. That matters because many infection-related cancers can be headed off before they ever gain momentum, especially when patients pay attention to symptoms like unusual bleeding, pain with swallowing, reflux, or persistent upper abdominal discomfort.
The big takeaway is not that everyday germs are hiding around every corner, but that some infections deserve real respect. When vaccines are available, when screening makes sense, and when symptoms do not go ignored, there is room to lower the odds in a pretty meaningful way.
