Protection of the susceptible requires use of all measures necessary to maintain or improve general health. The individual who has good mental and physical health has good resistance to disease. Good personal hygiene, including avoidance of known or suspected sources of disease, helps maintain health. A number of immunizing agents are available for use in conjunction with other measures for the control of some, but not all, communicable diseases. In some instances, suppressive drugs are available to decrease the severity of disease.