1.9 lakh cancers in India linked to infections every year: What to know

A WHO-IARC study has estimated that nearly 1.9 lakh new cancer cases in India each year are attributable to infections. The findings place vaccination, infection detection, treatment and screening at the centre of cancer prevention.

In Short

• Researchers assessed 12 proven cancer-causing infectious agents in the study
• HPV accounted for the largest share, with over one lakh cases
• Cervical cancer prevention remains possible through vaccination, screening and early treatment

Nearly 1.9 lakh new cancer cases in India every year can be attributed to infections, according to a new study by the World Health Organisation’s International Agency for Research on Cancer (WHO-IARC). With India recording an estimated 15.62 lakh new cancer cases in 2024, this means infections were linked to more than 12% of all new malignancies that year.

Globally, the study estimated that about 23 lakh, or 2.3 million, new cancer cases were attributable to infections.

The researchers examined 12 infectious agents classified as group 1 carcinogens – meaning there is sufficient evidence that they can cause cancer in humans.

These include human papillomavirus (HPV), Helicobacter pylori, hepatitis B and C viruses, Epstein–Barr virus (EBV), human immunodeficiency virus (HIV) and Kaposi's sarcoma-associated herpesvirus, among other infectious and parasitic agents.

But the term “attributable to” needs some context. The study does not mean that 1.9 lakh people simply contracted an infection and then developed cancer. The estimate is based on population-attributable fractions – a measure used to calculate how much of the cancer burden in a population can be linked to a particular risk factor.

Infections can increase cancer risk through several mechanisms. Some viruses can interfere directly with cellular processes, while chronic infections can cause prolonged inflammation, tissue damage and changes that, over years, may contribute to cancer development.

HPV: CERVIX TO THROAT

HPV is by far the biggest infection-linked contributor to India's cancer burden in the study, accounting for more than 1 lakh cases.

Its strongest and most established link is with cervical cancer. Persistent infection with certain high-risk HPV types can cause changes in cervical cells that, if not detected and treated, can eventually progress to cancer. India carries the highest burden of cervical cancer globally – recording nearly 80,000 new cases every year.

HPV is also linked to cancers of the oropharynx, which includes parts of the throat, tonsils and base of the tongue. These cancers can occur in both men and women.

“Cervical cancer is largely attributed to the HPV virus,” said Dr Mandeep Singh Malhotra, senior oncologist, adding that the virus is also known to cause oropharyngeal cancers.

The burden of HPV-related cancer is particularly significant because cervical cancer is one of the cancers for which prevention is possible through vaccination, screening and timely treatment of precancerous lesions.

The Union government this year launched an HPV vaccination campaign for 14-year-old girls across India and wider uptake of HPV vaccination is expected to alter the future burden of cervical cancer.

HEPATITIS: A LIVER CANCER LINK

Hepatitis B and C viruses together accounted for roughly 15,000 infection-attributable cancers in India in the study – about 10,000 linked to hepatitis B and 5,300 to hepatitis C.

Their major cancer connection is with the liver. Unlike an infection that clears quickly, chronic hepatitis can persist for years, causing ongoing inflammation and damage to liver cells. Over time, this can contribute to cirrhosis and hepatocellular carcinoma, the most common form of primary liver cancer.

Dr Malhotra pointed to the long-term nature of this process, noting that viral hepatitis can cause liver cancer when chronic infection develops over years. He also highlighted hepatitis C-associated liver cancer mainly being seen in Punjab.

The link also underlines why detecting and treating chronic viral hepatitis is relevant to cancer prevention, rather than viewing these infections only as liver diseases.

EBV, H. PYLORI AND MORE

EBV was associated with about 22,000 cases in India, according to the study. The virus is linked to several cancers, including nasopharyngeal cancer and certain lymphomas.

The geographical pattern can also matter.

Dr Malhotra pointed to the northeastern part of India, where EBV is more common, and said there has been a rise in nasopharyngeal cancers.

H. Pylori, meanwhile, accounted for roughly 47,000 infection-attributable cancers in India. The bacterium colonises the stomach and persistent infection can cause chronic inflammation and changes in the stomach lining, increasing the risk of gastric cancer. It has also been linked with some cancers of the lower oesophagus.

The list does not end there. Certain persistent infections have been investigated for their role in other cancers, including gallbladder cancer.

Dr Malhotra also pointed to emerging research around the oral microbiome – the community of microorganisms living in the mouth – and its possible contribution to oral cancer alongside established risks such as tobacco.

“The larger message from the study is therefore not that infections are responsible for a fixed share of every individual's cancer risk. Rather, it highlights a sizeable population-level burden that may be preventable or reducible,” said a researcher from the Indian Council of Medical Research - National Institute of Cancer Prevention and Research (ICMR-NICPR).

In India’s context, the evidence brings vaccination, infection detection, treatment, cancer screening and tobacco control into the same prevention conversation.

“While HPV vaccination can reduce the risk of HPV-related cancers, identifying and treating chronic hepatitis and H. pylori infections can potentially reduce the pool of people at risk of some infection-associated malignancies,” said the scientist.

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