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Risk for Cancer-Causing Infections Highest in Low- and Middle-Income Countries

Around the world, approximately 15% of can­cer cases are caused by infections.1 These in­fections include Helicobacter pylori (H pylori), human papillomavirus (HPV), Hepatitis B virus (HBV), Hepatitis C virus (HCV), Epstein-Barr virus, human herpesvirus 8 (HHV-8), Schistosoma haematobium, and human T-lympho-trophic virus type 1 (HTLV-1).

Cancer is a collection of related diseases with a common trait: the occurrence of abnormally growing cells that have the potential to invade and spread to other tissues.2 Cancer is the second leading cause of death around the world, with 8.8 million deaths (about 1 in 6) occurring in 2015.2 Cancer-related deaths in low- and middle-income countries account for 70% of all deaths from cancer in the world.2

One important risk factor for cancer that is not often discussed—unlike other risks such as tobacco use, ultra-violet radiation, and aging—is infection with a cancer-causing virus. Nearly 1 in 4 new cases of cancer in low- and middle-income countries is the result of a cancer-causing infection such as HPV or hepatitis compared to less than 1 in 10 new cases of cancer in high-income countries.1,2 Sub-Saharan Africa and East Asia are regions of the world with the highest rates of cancers attributed to carcinogenic infections, at 31% and 23%, respectively. However, only about 4% of new cases in North America and about 7% of new cancer cases in Europe are attributable to oncogenic infections.1

H pylori, HPV, HBV, and HCV are responsible for the majority (~92%) of cancers that are attributable to infec­tions worldwide, yet the proportions of cancers caused by these infections differ by region of the world.1 For instance, compared with high-income countries, low-and middle-income countries show a larger proportion of cancer cases related to infections attributed to HPV, HBV, and HHV-8. High-income countries, on the other hand, show a larger proportion of their cases attributed to H pylori and HTLV-1.1,3 There is geographic variation in both the range of rates of cancers caused by onco-genic infections and the types of infections that most commonly cause cancers and I explore these differences in the next several sections.3