The main diseases that threaten human health in today's society are _ _ _ _ diseases and cancer.

In the past, infectious diseases were once the main diseases that threatened human health. At present, in many developed countries and some developing China countries, the main diseases that affect human health are no longer infectious diseases. Cardiovascular and cerebrovascular diseases and cancer have become a kind of non-communicable diseases that pose the greatest threat to human health and life, and are called modern civilized diseases. Besides genetic and congenital factors, the factors that affect cardiovascular and cerebrovascular diseases and cancer also include people's lifestyles, such as smoking, drinking, overnutrition and staying up late.

So the answer is: cardiovascular and cerebrovascular diseases.