About 2.3 million new cancers in 2024, one in eight worldwide, were caused by infections, according to a World Health Organization (WHO) study published in The Lancet Oncology. Lung cancer is not one of them: no infection is an established cause of lung cancer, and its main avoidable causes remain smoking and air pollution. But infections still affect lung cancer in other ways, from uncertain evidence on human papillomavirus (HPV) to tuberculosis and symptoms that look like a chest infection.
This article sets out what the new research found, what the evidence says about infections and lung cancer, and what it means for prevention and early diagnosis in Europe.
Key points
About 12% of new cancers worldwide in 2024 were caused by infections, led by Helicobacter pylori and HPV.
Lung cancer is not counted among them, because no infection is an established cause.
HPV has been found in a small share of lung tumours, around 3% in pooled European data, but a causal link is unproven.
Past tuberculosis and pneumonia are both linked with a higher risk of lung cancer, though neither is proven to be a cause.
Lung cancer symptoms can be mistaken for a chest infection, which can delay diagnosis.
In this article
What did the new study on infections and cancer find?
Infections caused an estimated 2.3 million of the new cancer cases diagnosed worldwide in 2024, or about one in eight. The analysis was led by researchers at the International Agency for Research on Cancer (IARC), the WHO's cancer agency, and published in The Lancet Oncology on 28 September 2026.
Five infections accounted for almost all of these cancers:
Helicobacter pylori: about 760,000 cases, mainly stomach cancer.
HPV: about 750,000 cases, mostly cervical cancer, plus anal, genital and some head and neck cancers.
Hepatitis B virus: about 360,000 cases, mostly liver cancer.
Epstein-Barr virus: about 260,000 cases, including nasopharyngeal and some stomach cancers and Hodgkin lymphoma.
Hepatitis C virus: about 160,000 cases, mostly liver cancer.
More than three quarters of infection-related cancers occurred in low- and middle-income countries. The burden also varies within Europe. Infections caused about 10% of new cancers in central and eastern Europe, compared with 5% in western Europe and 4% in northern Europe.
"While this burden is enormous, it is also largely preventable," said lead author Dr Harriet Rumgay of IARC. A separate WHO and IARC analysis published in Nature Medicine in February 2026 ranked infections as the second leading avoidable cause of cancer worldwide, after smoking.
Is lung cancer caused by an infection?
No infection is an established cause of lung cancer, so lung cancer does not appear in the new estimates. The WHO and IARC analysis of avoidable cancer risks found that lung cancer is mostly linked with smoking and air pollution.
HIV is one example of how hard these links are to untangle. Studies have linked HIV with lung cancer, but when IARC researchers estimated the global burden of HIV-related cancers in 2025, they left lung cancer out. They cited a lack of consensus on how much of the link could be explained by smoking.
Can HPV cause lung cancer?
HPV has been found in some lung tumours, but there is no proof that it causes lung cancer. Results vary widely between countries and laboratories.
The largest pooled analysis, published in Carcinogenesis in 2014, combined data on 3,249 people with lung cancer from 27 studies. HPV16 or HPV18, the high-risk types behind most cervical cancers, was found in about 3% of lung tumours in Europe, 4% in North America, 5% in Asia and 22% in South and Central America. HPV was more likely to be found in tumour tissue than in healthy lung tissue. The authors said further work was needed to judge whether this reflected a causal relationship.
A 2024 systematic review of 97 studies covering 9,098 people found HPV rates in lung cancer ranging from 0% to 69%. European studies alone varied hugely: HPV was found in 3 of 223 tumours in a Dutch study, none of 80 in a Czech study, 3.9% of 334 samples in Norway and 19% of 100 people in Greece. In one larger European study, HPV DNA was present in almost 10% of tumours, but none showed signs that the virus's cancer-causing genes were active. The reviewers concluded that "causal associations remain uncertain".
IARC's estimates do not count any lung cancers as caused by HPV. The uncertainty also reflects how much is still unknown about the causes of lung cancer in people who have never smoked.
Tuberculosis and lung cancer risk
People who have had tuberculosis (TB) have a modestly higher risk of later being diagnosed with lung cancer. A 2022 meta-analysis in the European Respiratory Review, which took account of age and smoking, found a 51% higher risk of lung cancer in cohort studies, with similar results from case-control studies.
The risk was highest in the first two years after a TB diagnosis. The authors note that some of these cancers may already have been present when TB was diagnosed, so the link cannot yet be shown to be causal. It also shows how easily the two conditions can be confused, because they share symptoms such as a long-lasting cough and weight loss.
Pneumonia, sepsis and COVID-19: what is the link with lung cancer?
A past episode of pneumonia is linked with a higher risk of lung cancer, but as with tuberculosis, the link does not prove cause. A pooled analysis by the International Lung Cancer Consortium, published in the American Journal of Epidemiology in 2012, found that people who had had pneumonia had a 57% higher risk of lung cancer, based on 12 studies. Higher risks were also seen in people who had never smoked, and the authors concluded that previous lung diseases influence lung cancer risk independently of tobacco use. As with any study of this kind, some pneumonias may have been an early sign of a cancer that had not yet been diagnosed.
The evidence for sepsis is weaker. A 2019 study in Clinical Infectious Diseases compared more than 1.8 million older adults diagnosed with cancer in the United States with 200,000 people without cancer. It found slightly higher odds of lung cancer in people who had been in hospital with sepsis (odds ratio 1.17). The authors said some of the links they found may reflect existing conditions or how cancers come to be diagnosed, rather than sepsis itself.
COVID-19 is not known to cause lung cancer, but it hit people with lung cancer hard. The international TERAVOLT registry collected data on 200 people with thoracic cancers, mostly lung cancer, in eight countries early in the pandemic. A third (33%) died, according to results published by Dr Marina Chiara Garassino and colleagues in The Lancet Oncology in 2020.
Respiratory infections may also affect cancer that has already spread. In a 2025 study published in Nature, researchers in the United States and at UMC Utrecht in the Netherlands found that flu and COVID-19 infections woke dormant breast cancer cells in the lungs of mice. In UK Biobank data, people with a history of cancer who caught COVID-19 in 2020, before vaccines were available, were about twice as likely to die of their cancer in the following two years. This research concerns cancer spreading to the lungs rather than lung cancer itself, and the researchers stress that a causal link in people is not yet proven.
When lung cancer looks like a chest infection
Lung cancer symptoms often overlap with those of chest infections, which can delay diagnosis. A persistent cough, breathlessness or an infection that will not clear can all be signs of lung cancer.
Some guidance recognises this. In England, the National Institute for Health and Care Excellence (NICE) says people aged 40 and over who have a chest infection that does not clear, or keeps coming back after treatment, may be offered a chest X-ray to check for lung cancer.
Lung Cancer Europe's Get Checked! campaign focuses on primary care in 2026, because family doctors are often the first to see these symptoms. Recognising when a chest infection may be something more is one of the most practical steps towards earlier diagnosis across Europe.
What this means for lung cancer prevention in Europe
Infection-related cancers already have clear EU prevention targets. In June 2024, EU Member States adopted a Council Recommendation on vaccine-preventable cancers, aiming to vaccinate 90% of girls against HPV and significantly increase vaccination of boys by 2030.
Lung cancer has no vaccine, so prevention depends on reducing smoking and air pollution and finding cancer earlier. Lung Cancer Europe wants the same level of ambition for lung cancer: strong tobacco control, cleaner air and fair access to lung cancer screening across Europe.
Frequently asked questions
What share of cancers are caused by infections?
About one in eight new cancers worldwide in 2024, or 2.3 million cases, were caused by infections, according to IARC. The share is lower in western and northern Europe, at about 4 to 5%, and around 10% in central and eastern Europe.
Does HPV cause lung cancer?
There is no proof that HPV causes lung cancer. HPV has been found in a small share of lung tumours, around 3% in pooled European data, but studies vary widely and researchers say a causal link remains uncertain.
Can a chest infection be a sign of lung cancer?
Yes. Lung cancer can cause symptoms that look like a chest infection, including a persistent cough or an infection that keeps coming back. In England, NICE guidance says people aged 40 and over with a chest infection that will not clear may be offered a chest X-ray.
Does pneumonia increase the risk of lung cancer?
People who have had pneumonia have a higher risk of later being diagnosed with lung cancer, about 57% higher in a large pooled analysis of 12 studies. Researchers cannot yet say whether pneumonia causes lung cancer, and some pneumonias may be an early sign of a cancer not yet found.
Is tuberculosis linked to lung cancer?
Yes, people who have had tuberculosis have a modestly higher risk of lung cancer, according to a 2022 meta-analysis. The risk is highest in the two years after diagnosis, and researchers cannot yet say whether TB causes lung cancer.
Summary
Infections cause one in eight cancers worldwide, and much of that burden could be prevented with vaccination, testing and treatment. Lung cancer is not part of that picture: it remains driven mainly by smoking and air pollution, and the evidence on HPV is uncertain. Where infections do affect lung cancer is in diagnosis, because symptoms that look like a chest infection can hide it. Earlier diagnosis in primary care and ambitious prevention policy remain the priorities.
About Lung Cancer Europe
Lung Cancer Europe is a pan-European advocacy organisation working for equal access to high-quality lung cancer care across Europe. Our members are national lung cancer advocacy organisations, and we bring their evidence and experience to European policymakers. Through our annual Lung Cancer Europe Reports, our Charter and the Get Checked! campaign, we work to improve diagnosis, treatment and support for everyone affected by lung cancer.
References
Rumgay H, et al. Global burden of cancer attributable to infections in 2024: a worldwide incidence analysis. The Lancet Oncology. 28 September 2026. Article
International Agency for Research on Cancer. Global burden of cancer attributable to infections in 2024: one in eight cancers worldwide linked to infections. Press release. 28 September 2026. Press release
Healio. 1 in 8 cancers attributable to infections; burden "enormous" but "largely preventable". 29 September 2026. Article
The ASCO Post. WHO analysis finds many global cancer cases attributable to modifiable risk factors (Nature Medicine). February 2026. Article
Huang Y, Georges D, Rumgay H, Soerjomataram I, Clifford GM. Global burden of cancer attributable to HIV: a worldwide incidence analysis. Lancet Global Health. 2025;13(9):e1525-e1532. Article
Ragin C, et al. HPV-associated lung cancers: an international pooled analysis. Carcinogenesis. 2014;35(6):1267-1275. Article
Sequeira T, et al. HPV and lung cancer: a systematic review. Cancers (Basel). 2024;16(19):3325. Article
Cabrera-Sanchez J, et al. Lung cancer occurrence after an episode of tuberculosis: a systematic review and meta-analysis. European Respiratory Review. 2022;31(165):220025. Article
NICE. Suspected cancer: recognition and referral (NG12). Information for the public: chest. Guidance
European Commission. EU steps up fight against vaccine-preventable cancers under Europe's Beating Cancer Plan. 21 June 2024. News
Brenner DR, Boffetta P, Duell EJ, et al. Previous lung diseases and lung cancer risk: a pooled analysis from the International Lung Cancer Consortium. American Journal of Epidemiology. 2012;176(7):573-585. Abstract
Liu Z, Mahale P, Engels EA. Sepsis and risk of cancer among elderly adults in the United States. Clinical Infectious Diseases. 2019;68(5):717-724. Abstract
Garassino MC, Whisenant JG, Huang LC, et al. COVID-19 in patients with thoracic malignancies (TERAVOLT): first results of an international, registry-based, cohort study. The Lancet Oncology. 2020;21(7):914-922. Article
Chia SB, Johnson BJ, Hu J, et al. Respiratory viral infections awaken metastatic breast cancer cells in lungs. Nature. 2025;645:496-506. Abstract and UMC Utrecht news