12 Infections Linked to 1 in 8 Cancer Cases Worldwide, Lancet Study Finds
By Fatima Raza · Health Desk · Updated October 15, 2026 One in every eight cancers diagnosed in the world last year was linked to an infection. A landmark analysis by the World Health Organization’s International Agency for Research on Cancer (IARC), published in The Lancet Oncology, found that 12 infectious agents classified as Group…
One in every eight cancers diagnosed in the world last year was linked to an infection. A landmark analysis by the World Health Organization’s International Agency for Research on Cancer (IARC), published in The Lancet Oncology, found that 12 infectious agents classified as Group 1 human carcinogens were responsible for around 12 per cent of all new cancer cases worldwide in 2024 — roughly 2.3 million diagnoses. Five infections account for nearly all of them: Helicobacter pylori (~760,000 cases), human papillomavirus or HPV (~750,000), hepatitis B (~360,000), Epstein-Barr virus (~260,000) and hepatitis C (~160,000).
Quick facts
- Study: IARC (WHO) analysis, published in The Lancet Oncology, October 2026
- Headline figure: 12% of new cancers worldwide in 2024 — 2.3 million cases, about 1 in 8
- Agents assessed: 12 pathogens classified as Group 1 (known) human carcinogens
- Top five: H. pylori, HPV, hepatitis B, Epstein-Barr virus, hepatitis C
- Inequality: 77% of infection-related cancers occurred in low- and middle-income countries
- Key message: Many of these cancers are preventable through vaccines, screening, antibiotics and antiviral treatment
What the Lancet study actually measured
This is not a guess built on old data. The IARC team looked at global cancer data from 2024 and estimated how many new cases could be attributed to infections already classified as known causes of cancer in humans. The figure that came out — 12 per cent, 2.3 million diagnoses — is the largest single update to this question in years, and it folds in newer evidence, including the link between Epstein-Barr virus and certain stomach cancers.
Dr Harriet Rumgay, a scientist in IARC’s Cancer Surveillance Branch and a co-author, said the findings underline how much infection control can contribute to reducing the global cancer burden — and how unevenly that burden falls. Despite progress in vaccination and screening, she noted, infection-related cancers remain a major global challenge, with the weight carried disproportionately by low- and middle-income countries.
The five infections behind nearly every case
1. Helicobacter pylori — ~760,000 cases (4% of all cancers)
The single largest contributor is a stomach bacterium most people have never heard of, picked up through contaminated food and water. H. pylori causes long-term inflammation in the stomach lining and is the main driver of non-cardia gastric cancer — cancer of the lower stomach. It is also one of the most treatable items on this list: a course of antibiotics can eradicate the infection.
2. Human papillomavirus (HPV) — ~750,000 cases (4%)
HPV is the primary cause of cervical cancer and is also behind cancers of the oropharynx, anus, penis, vagina and vulva. This is the infection where prevention has worked best: the HPV vaccine protects against the high-risk types responsible for most cervical cancers, and screening can catch cervical cell changes before they ever become invasive. Where vaccination and screening reach people, these cancers are already falling.
3. Hepatitis B virus (HBV) — ~360,000 cases (2%)
Transmitted through blood, sexual contact and from mother to child, chronic hepatitis B infection is one of the two big drivers of liver cancer. The hepatitis B vaccine — routinely given to newborns in many countries — breaks this chain early, which is why its absence in some regions shows up in the cancer figures decades later.
4. Epstein-Barr virus (EBV) — ~260,000 cases (1%)
EBV is the odd one out: a herpesvirus carried by more than 90 per cent of adults, most of whom will never have a problem with it. It is linked to nasopharyngeal carcinoma, certain gastric cancers and some lymphomas. The study incorporated newer evidence connecting EBV to additional stomach cancer types, which pushed its share up in this updated analysis.
5. Hepatitis C virus (HCV) — ~160,000 cases
A bloodborne virus causing chronic hepatitis and liver cancer. Hepatitis C has no vaccine — but it has something almost as good: modern antiviral treatment cures most infections. Curing the virus removes the ongoing liver damage that, over years and decades, can turn into cancer.
The other seven: rarer, but still counted
The remaining infections on the IARC list each contribute a smaller share: Kaposi’s sarcoma-associated herpesvirus (KSHV, ~35,000 cases), human T-cell lymphotropic virus type 1 (HTLV-1, ~3,900 cases, causing adult T-cell leukaemia/lymphoma), the parasitic flatworm Schistosoma haematobium (~5,900 cases, bladder cancer), two liver flukes (Opisthorchis viverrini and Clonorchis sinensis, both causing bile duct cancer), Merkel cell polyomavirus (~3,200 cases of an aggressive skin carcinoma) and HIV (~2,300 direct cases, plus tens of thousands more indirectly through immune suppression).
Rare does not mean irrelevant. In the regions where these infections are common — parts of Southeast Asia for the liver flukes, sub-Saharan Africa for the schistosome — they are among the most concrete cancer risks a person faces, and several are treatable or preventable.
Why this matters more in countries like Pakistan
The study’s most uncomfortable finding is the geography: about 77 per cent of infection-related cancers occurred in low- and middle-income countries. That gap comes down to differences in infection rates, vaccination coverage, screening programmes, access to testing and availability of treatment.
Pakistan sits squarely in the high-burden zone. Hepatitis B and C are widespread, HPV vaccination is still catching up, and H. pylori is common — which means the exact levers the study highlights (vaccination, screening, treatment) are the ones that need scaling here. For a Pakistani reader, the takeaway is practical rather than alarming: the hepatitis B vaccine exists, hepatitis C is curable, H. pylori is treatable, and cervical screening saves lives. The barriers are access and awareness, not science.
How an infection actually becomes cancer
The study is careful on a point worth repeating: most infected people never develop cancer. What raises the risk is persistence — an infection that the body never clears, smouldering for years or decades. Chronic hepatitis B and C grind away at the liver. High-risk HPV, if it persists, can push cervical cells through changes that become cancerous if never detected. H. pylori keeps the stomach inflamed year after year.
The route is the same each time: long-term inflammation or cell damage, slowly accumulating genetic changes, and eventually a cell population that stops playing by the rules. That is why the prevention story is so strong here — interrupt the infection early enough, and the whole chain never starts.
The bottom line
We tend to think of cancer as bad luck, bad genes or bad habits. This study adds a fourth category that is, in many ways, the most hopeful: infections we can vaccinate against, test for, treat and sometimes cure. Two-point-three million cancers a year is a staggering number — but a meaningful share of them were never inevitable. They were waiting on a vaccine, a screening visit, or a course of medicine.
Also read on TimelyUps
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- Pakistan Stops Issuing Machine-Readable Passports From Today — E-Passports Only From October 15, 2026 — the week’s other major Pakistan story.
Frequently asked questions
Can infections really cause cancer?
Yes — certain persistent infections are established causes of specific cancers. According to the IARC analysis published in The Lancet Oncology, 12 infectious agents classified as known human carcinogens were linked to about 12% of new cancer cases worldwide in 2024, roughly 2.3 million diagnoses.
Which infections are linked to cancer?
The five biggest contributors are Helicobacter pylori (~760,000 cases, mainly stomach cancer), HPV (~750,000, mainly cervical cancer), hepatitis B (~360,000, liver cancer), Epstein-Barr virus (~260,000, nasopharyngeal, gastric and lymphoma cancers) and hepatitis C (~160,000, liver cancer). Seven rarer agents make up the rest.
Does having one of these infections mean I will get cancer?
No. Most people who carry these infections never develop cancer. Risk depends on the type of infection, how long it persists, the immune response and other factors. The study stresses that infection-linked does not mean inevitable.
Can infection-related cancers be prevented?
Many can. The HPV vaccine guards against the virus types behind most cervical cancers; the hepatitis B vaccine prevents chronic HBV infection; hepatitis C, while vaccine-less, is curable with antiviral treatment; and H. pylori can be eradicated with antibiotics. Screening programmes also catch cervical changes before they turn cancerous.
Why do low-income countries carry 77% of the burden?
The IARC analysis links the imbalance to higher infection rates combined with lower vaccination coverage, weaker screening programmes, limited access to testing and less availability of treatment in low- and middle-income countries.
This article provides general health information only and is not a substitute for professional medical advice. Always consult a qualified doctor for personal health concerns.
