Sexually Transmitted Infections (S.T.Is) are those diseases which are transmitted though hetero/homosexual contact. It is also referred to as Sexually Transmitted Diseases (S.T.Ds)

The risk of transmission is increasing in case of unprotected sex.

Although called as S.T.Is; yet these infections (HIV/Hepatitis B, and Hepatitis C) have also other routes of transmission; which includes: Shared needles in Drug of Abuse, Tattoos, surgery and even barbershops and beauty & nail care spas.

The most common infections are: HIV (human immunodeficiency virus), HBV (Hepatitis B Virus), HCV (Hepatitis C Virus) and Syphilis.

Syphilis, unlike HIV, HBV and HCV, is a Bacterial Infection.

Each of these infections has a "Window Period". The window period is the time between contracting the infection, until the time it can be detected. During this period, the infectious agent multiplies within the host and increase in number.

Window periods varies between various infectious agent and ranges between 21 days (for HIV) and 28 days (for HBV, HCV and Syphilis).

Some infectious agents are more virulent than others (i.e. they are more capable of causing infection and being transmitted even during the window period). The most virulent infection is the Hepatitis B Virus.