When a disease occur in single individuals or localized groups is called: Epidemic Sporadic Endemic Pandemic

The correct term for a disease that occurs in single individuals or localized groups is Sporadic.

Explanation:

1. Epidemic: This refers to an outbreak of a disease that spreads rapidly and affects a larger number of individuals in a specific geographic area or population during a specific time period.

2. Sporadic: This denotes cases of disease that are scattered or isolated rather than being widespread. A sporadic disease occurs infrequently and irregularly and typically affects a few individuals or local areas.

3. Endemic: This refers to a disease or condition regularly found among particular people or in a certain area. It is consistently present in a population.

4. Pandemic: This is an outbreak of disease that occurs over a large geographic area, often worldwide, affecting a substantial proportion of the population.

In summary, a disease confined to small groups or occurring irregularly is best described as Sporadic.