Cancers we can prevent

The HPV virus in a pap smear.

One in every six cancer deaths worldwide is caused by preventable infections, a total of 1.5 million deaths yearly that could be halted by widespread vaccination programs, researchers report. 

Since 1990, that number has grown by about half a million, suggesting that vaccination programs are losing ground in the battle rather than gaining it. The vast majority of the cases are caused by three viruses and a bacterium, which are the leading causes of gastric, liver and cervical cancers. Cervical cancers account for about half of the infection-related cancers in women, while liver and gastric cancers account for about 80% of those in men.

Cervical cancers are caused primarily by the human papilloma virus (HPV), as are anal and penile tumors. Stomach cancers are caused by the bacterium Helicobacter pylori. The hepatitis B and hepatitis C viruses cause liver cancer. All such infections are readily preventable by vaccination. Other less common agents include the Epstein-Barr virus, which causes nasopharynx tumors and Hodgkin's lymphoma; human herpes virus type 8, which causes Kaposi's sarcoma, usually in conjunction with HIV; and the parasite Schistosoma haematobium, which causes bladder cancer.

The researchers reported that the worldwide average of cancers caused by infectious agents was 16.5%, with about three times more (22.9%) occurring in developing countries than in developed countries (7.4%). Rates varied widely between regions, ranging from a low of 3.3% in Australia and New Zealand to a high of 32.7% in sub-Saharan Africa. About 4% of cancers were caused by infectious agents in North America and 7% in Europe.

(Thanks, Jack Marler)