Also includes infection-related factors, such as sanitation and proximity to people, animals, or insects. The genes you inherit can affect how likely you are to get a disease, and how that disease may affect you. If a person is genetically susceptible to a particular disease, that person's risk of getting the disease is higher. Genetic susceptibility combines with environmental input to produce disease. But the combination need not be half and half.
Genes can cause a slight susceptibility or a strong susceptibility.
If the genetic contribution is weak, the environmental influence must be strong to produce disease, as we show in the diagram below. Here are a few examples of diseases that have some genetic contribution and some environmental contribution. Genetic susceptibility is part of a spectrum of factors, including age and general health, that contribute to disease or protect against it. They divide into new cells for a limited part of their lifespan. By contrast, cancer cells seem to have no limit on their lifespan or their ability to divide into new cells.