An estimated 2.3 million new cancer cases worldwide in 2024, accounting for 12% of the total, were linked to infections, according to an analysis by researchers at the International Agency for Research on Cancer (IARC), the World Health Organization’s cancer research agency, published in The Lancet Oncology.

“Infectious agents are an important preventable cause of cancer globally,” the researchers stated in the paper.

The team used 2024 data from the Global Cancer Observatory and studied 12 infectious agents that IARC classifies as proven causes of cancer in humans. These include the bacterium Helicobacter pylori (H. pylori), human papillomavirus (HPV), hepatitis B and C viruses, Epstein-Barr virus (EBV) and HIV. For each infection and cancer pair, it estimated the share of cases caused by the infection.

H. pylori accounted for the largest number of cases, at about 7.6 lakh, followed by HPV at 7.5 lakh. Hepatitis B was linked to 3.6 lakh cases, EBV to 2.6 lakh and hepatitis C to 1.6 lakh. Of the HPV related cases, 6 lakh were cervical cancer.

Low- and middle-income countries accounted for 77 percent of these cases. Eastern Asia had the largest number, at 9.9 lakh cases, or 42 percent of the global total. Sub-Saharan Africa had the highest share of cancers linked to infections, at 25 percent.

The main paper reports figures by region rather than by country. India falls in south-central Asia, where an estimated 2.8 lakh cancer cases in 2024 were linked to infections. That was 12 percent of all cancers in the region, the same as the global share. After adjusting for age, the region’s rate of 13.3 cases per 100,000 people a year was among the lowest of any region.

HPV was the biggest driver in the region, linked to 1.3 lakh cases, or 6 percent of all cancers there. India accounted for 77 percent of these cases, or about 1 lakh. India’s rate of 6.8 per 100,000 was close to the regional average of 6.3.

The study listed vaccination, screening and treatment among proven ways to prevent these cancers. HPV types 16 and 18 account for nearly three-quarters of cervical cancer cases globally. Vaccination and HPV testing during cervical screening are at the core of the WHO’s global strategy to eliminate cervical cancer. Single-dose vaccination programmes are expected to improve uptake, because one dose has been found to work as well as two or three doses.

The authors said HPV vaccine coverage still needs to improve greatly in low- and middle-income countries to avoid widening gaps in future cervical cancer burden. Because HPV also causes cancers in men, vaccinating both boys and girls is recommended in countries with enough resources.

For liver cancer, which made up most hepatitis related cases, the WHO has launched an initiative to eliminate viral hepatitis. It includes newborn hepatitis B vaccination, safe injection practices, and testing and antiviral treatment for hepatitis B and C.

For H. pylori, Japan, South Korea and China run stomach cancer screening using endoscopy, an internal examination of the stomach. The study said endoscopy is invasive and costly, which limits wider use.

The authors noted that the estimates do not include ranges showing how far the figures could be off. They also said high-quality cancer registries cover only about 19 percent of the global population and 2 percent of Africa’s, which could lead to over- or underestimation.

The authors said many prevention measures are cost-effective but remain underused because of social, financial and political barriers, often in the settings that need them most.

What are experts saying?

Dr Srinivasa B J, Senior Consultant, Medical Oncology, HCG Cancer Hospital, K R Road, Bengaluru, said preventive steps can change the outlook for HPV-linked cancers.

“What makes these HPV related cancers problematic is not just the infection but the persistence of some infections for many years owing to the failure to vaccinate, screen, and treat precancerous lesions in time,” he said.

He said India’s nationwide HPV vaccination programme, launched in 2026, targets around 12 million adolescent girls aged 14. “Our main task is to reach all eligible females, especially those in rural, remote, and poor regions.”

“A woman need not wait until she develops any symptoms to think of cervical cancer screening because precancerous cervical lesions do not produce any symptoms,” Dr Srinivasa noted on screening.

He said not every Indian needs testing for H. pylori, and the focus should be on people with gastrointestinal diseases or a high risk of gastric cancer.

Dr Srinivasa said the National Viral Hepatitis Control Programme offers free hepatitis B and C diagnosis and treatment. According to government statistics, more than 21 crore people have been screened and over six lakh are under treatment, he mentioned.

“The task now is to detect individuals affected by these diseases and connect them with appropriate healthcare,” he said.

Dr Srinivasa also pointed out that it is very important for parents to make sure that their children and teenagers are properly vaccinated against HPV and have received their hepatitis B vaccine shots.”

“Women should continue cervical cancer screening after vaccination,” he added.

Also read: Men in Northeast India facing a higher cancer burden