Many infectious diseases can be controlled and even they can be eradicated if we follow the principles of prevention. These principles are very simple but need dedication and awareness in implementing them in the routine practice. Immunization is possible to prevent many infectious diseases by artificially exposing the person to the killed or live attenuated bacteria or viruses, who is not exposed to these infectious agents before. When the person is given either whole bacteria or viruses or its components, the individual resistance power gets boosted up and subsequently he will be prevented from developing the diseases even if he comes in contact with the infectious agent. A well-balanced nutritious diet helps in preventing many infectious diseases. Malnutrition is one of the important factors that decides the outcome of many diseases like diarrheas, tuberculosis, and other similar diseases.