One in six cancers worldwide are caused by treatable infections.
A study by the International Agency for Research on Cancer found that bacteria, viruses and parasites cause around two million cases of cancer each year.
Plus, preventable or treatable infections account for 1.5 million of the 7.5 million global deaths from cancer since 2008, the Lancet Oncology reported.
In women, cervical cancers accounted for around half of all cancers caused by infections, while in men infections caused 80 per cent of liver, stomach and colon cancers.
Perhaps unsurprisingly, the proportion of cancers caused by infections was higher in developing countries than in the developed world.
Catherine de Martel and Martyn Plummer from the International Agency for Research on Cancer said that infections were one of the biggest and preventable causes of cancer in the world.
"Application of existing public-health methods for infection prevention, such as vaccination, safer injection practice, or antimicrobial treatments, could have a substantial effect on future burden of cancer worldwide," they said.
In the UK around 309,500 new cases of cancer are diagnosed each year.
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