What is a way to prevent epidemics of contagious diseases?

This would depend on the type of disease, whether it is spread through air, water, blood, etc, but there are several things that can be done. If someone is around a diseased person, they should wear protective things such as gloves and a face mask. Also, if spread by blood, do not come into contact with blood and wear mosquito spray. Also do not collet stray feathers from wild birds or touch dead animals, as they could be carrying disease. Have your pets and self vaccinated and never use a dirty needle. Also wash hands. It helps if the country you are in checks all immigrants and travelers for disease before their entry so that diseases will be less easily passed through borders. Make sure drinking water is clean along with food.