In many states it is a criminal offense to intentionally or recklessly transmit a sexually transmitted disease (STD or venereal disease) to another person. Examples of such diseases include HIV/AIDS, syphilis, gonorrhea, chlamydia, genital herpes, human papillomavirus (HPV), genital warts, and hepatitis B.

Laws vary from state to state, and in some states these laws include other infectious or communicable diseases. In some states there is a specific criminal offense for transmission of sexually transmitted or communicable diseases, and in other states criminal prosecutors charge the defendant with a more general crime like assault.

Laws regarding criminal liability for the intentional or reckless transmission of sexual or other infectious or communicable diseases are generally located in a state’s statutes—often in the penal or criminal code, or the health and safety code.

A person who negligently transmits a sexually transmitted disease to another person through sexual contact—without informing the other person of the offender’s infection before the sexual contact—may also be subject to civil liability for money damages in a lawsuit.

In California, it is a criminal offense to willfully expose another person to HIV, which is considered a sexually transmitted disease (STD). Under California Health and Safety Code Section 120291, individuals who are aware that they are infected with HIV and who intentionally engage in conduct that poses a substantial risk of transmission to another person can be charged with a felony. This law was updated in 2017 to reduce the penalty from a felony to a misdemeanor, except in cases where the transmission was intentional. Other STDs are not specifically covered by this statute, but transmission of other diseases may be prosecuted under California's general criminal laws, such as those for battery or assault. Additionally, individuals who negligently transmit an STD may face civil liability and be sued for damages. It is important for individuals to disclose their STD status to sexual partners, as failure to do so can result in both criminal charges and civil lawsuits.