Cancer can seem random.
asserted
Cancer → seem → ?
It’s often the result of many factors, including genetic mutations that build up over a lifetime of exposure to sun, pollution, and other sources of DNA damage, combined with a person’s genetic predisposition.
asserted
that → ’ → predisposition
DNA damage accumulated over time can weaken the body’s ability to suppress out-of-control cell growth, which is how tumors form.
asserted
tumors → accumulate → growth
Uncovering the links between certain infections and cancers raises the hope that by preventing infection, one could prevent certain malignancies.
uncertain
one → uncover → malignancies
A recent report from the World Health Organization’s International Agency for Research on Cancer (IARC) published in the Lancet Oncology found that 12% of new cancer cases in 2024—the most recent year for which data were available—were caused by 12 infections.
asserted
data → publish → infections
Which infections are associated with cancer?
asserted
infections → associate → cancer
Certain human papillomaviruses, or HPV, are behind the majority of cervical cancers and a number of head and neck cancers as well, says Harriet Rumgay, an epidemiologist at IARC who is an author of the new report.
asserted
who → say → report
About 4% of new cancer diagnoses in 2024 could be attributed to HPV infection.
uncertain
% → attribute → infection
Doctors and researchers have known for decades that hepatitis B and hepatitis C infections also drive many cases of liver cancer, linked to 2% and less than 1% of new diagnoses respectively, according to the report.
uncertain
infections → know → report
There is also strong evidence linking Helicobacter pylori, a bacterium that infects the stomach and small intestine, with gastric cancers.
asserted
that → be → cancers
This infection was calculated to be behind about 4% of new diagnoses.
asserted
infection → calculate → diagnoses
And Epstein-Barr Virus (EBV), which causes mononucleosis and affects more than 90% of the world’s population, was involved in around 1% of new diagnoses, including lymphomas, nasopharyngeal cancers, and gastric cancers.
asserted
which → cause → lymphomas
Seven other infections, including HIV, were also flagged as carcinogens in the study.
asserted
infections → include → study
Most people who have these infections will not develop cancer.
asserted
who → have → cancer
It’s not also immediate—there may be a years-long delay.
uncertain
It → ’ → ?
And infection is often only one of a number of factors contributing to a given cancer.
asserted
infection → contribute → cancer
For instance, when it comes to the relatively high rates of EBV-driven nasopharyngeal cancers in China, researchers believe that some genetic predisposition and environmental factors are also involved.
asserted
predisposition → come → China
Why do some infections cause cancer?
asserted
infections → cause → cancer
It depends on the infection.
asserted
It → depend → infection
In the case of HIV, the virus suppresses the immune system, making it easier for other carcinogenic viruses to replicate.
asserted
viruses → suppress → system
H. pylori causes tissue damage and produces toxins that destabilize the body’s natural control of cellular growth and division, which can lead to cancer.
asserted
which → cause → cancer
With EBV, says Claire Shannon-Lowe, a virologist at the University of Birmingham in the U.K. who studies EBV and cancer but was not involved in the research, it has to do with how the virus hides within immune cells called B cells.
asserted
virus → say → cells
“It's a whole host of things that the virus itself is doing to the B cell to make it continually grow,” she says.
asserted
she → do → cell
That includes blocking normal cellular housecleaning procedures that would both root the virus out and arrest cancer development.
asserted
that → include → development
How can these cancers be prevented?
asserted
cancers → prevent → ?
Some of these infections have treatments.
asserted
Some → have → treatments
H. pylori can be cleared with antibiotics, for example, reducing the risk of gastric cancer, and treating HIV reduces cancer risk from the infection as well.
asserted
treating → clear → infection
Some other infections on the list have vaccines.
asserted
infections → have → vaccines
In fact, for some of these vaccines, cancer prevention was a major goal driving their development.
asserted
prevention → drive → development
“The hepatitis B virus vaccine was the first vaccine that was developed against cancer,” says Rumgay.
asserted
Rumgay → develop → cancer
Likewise, the HPV vaccine, which was approved 20 years ago, is intended to prevent cervical cancer.
asserted
which → approve → cancer
Cancer epidemiologists may start seeing the effects of widespread HPV vaccination in future analyses, Rumgay says.
uncertain
Rumgay → start → analyses
“More and more people who have been vaccinated are starting to reach the age where we would potentially see the impact on cervical cancer rates or other cancer rates,” she says.
asserted
she → vaccinate → rates
For EBV, a nearly ubiquitous virus with a long, clearly documented history of contributing to cancer, “we don't have an effective vaccine yet, or an effective way of preventing it,” says Rumgay.
asserted
Rumgay → document → it
“This is something that we want to highlight with our study.
asserted
we → want → study
Historically, it was difficult to interest pharmaceutical companies in vaccines for viruses like EBV that are common and nonlethal, says Lawrence Young, a virologist and emeritus professor of molecular oncology at University of Warwick in the U.K. who has spent his career studying cancer and EBV.
asserted
who → interest → cancer
(Young was not involved in the IARC research.)
asserted
Young → involve → research
But thanks in part to research suggesting EBV might be involved in multiple sclerosis, an autoimmune disorder, “they've all become very interested,” he says.
uncertain
he → suggest → sclerosis
A number of vaccine candidates are now being studied, with some in clinical trials.
asserted
number → study → trials
For some of the infections implicated by the latest study—the Kaposi-sarcoma associated herpes virus, in particular—there’s need for much more research into prevention, says Rumgay.
asserted
Rumgay → implicate → prevention
…and 1 more, not listed.
The Aporia
