Viral and bacterial infections passed from one person to another through sexual contact.

Adolescence is the period of transition from childhood to adulthood when profound changes occur. This period of tremendous change fulfills important developmental tasks in which the adolescent develops formal operational thought, builds cognitive decision-making skills, forms a sense of self-identity, and expresses the need for autonomy and individuation from the family.

Adolescence is also a time of opportunities and risk, when many health behaviors are established. Although many of these behaviors are health-promoting, some are health-compromising, resulting in increasingly high rates of adolescent morbidity and mortality. For example, initiation of sexual intercourse and experimentation with alcohol and drugs are normative adolescent behaviors. However, these behaviors often result in negative health outcomes such as the acquisition of sexually transmitted diseases (STDs), including the fatal human immunodeficiency virus (HIV). As a...