The interest in the connection shown by the author and confirmed by others between breeding tropical birds and cancer has expanded to the health risks of the intensive rearing of poultry, pigs and cattle for consumption. Since the fifties of the 20th century, intensive breeding in livestock has increased sharply. An increase that keeps pace with the recent increase in cancer mortality.In the past many large and small mammals have been domesticated. The population has acquired immunity against the great epidemics of the past. Zoonotic infections like the black plague, smallpox, tuberculosis, measles, typhoid and cholera could be treated with vaccination and antibiotics.Since the middle of the twentieth century we have a new situation, caused by intensive farming. All meat of farmed mammals is only produced by manual insemination of cattle, pigs and rabbits. Mad cow disease, swine fever and bird flu are the result of intensive livestock farming. The population is now confronted with a new type of more intensive and intracellular infections with RNA-viruses. Batteries of laying hens and broilers spread leukemia virus in raw egg proteins. Meat cows and dairy cows spread leukemia viruses in the food chain. Fast food, unnatural food and hamburger consumption lead to obesity and chronic diseases. In the meantime, the number of cancer diseases is increasing and is nowadays prime cause of chronic diseases and premature death in the elderly.