The Search for Infectious Causes of Human Cancers: Where and Why?

Slightly more than 20% of the global cancer burden can currently be linked to infectious agents, including viruses, bacteria and parasites. This manuscript analyses reasons for their relatively late discovery and highlights epidemiological observations that may point to the involvement of additional infectious agents in specific human cancers. Emphasis is placed on haematopoietic malignancies, breast and colorectal cancers, but also basal cell carcinomas of the skin and lung cancers in non-smokers.