A single disease health insurance plan is just as it sounds. It is a plan that is designed to only cover one disease. This type of insurance plan is available to cover a range of extremely serious illnesses such as cancer and multiple sclerosis. Make sure when you are gathering your individual health insurance quotes that you are not being quoted prices on single disease insurance plans, unless that is what you are specifically seeking. These plans will not cover routine or emergency health care costs, other than for the single illness defined in the policy.