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 Montana, the transmission of a sexually transmitted disease (STD) can lead to criminal charges under certain circumstances. Montana Code Annotated §45-5-207 outlines that it is a felony for a person to knowingly expose another to an STD without their informed consent. This applies to diseases such as HIV/AIDS, syphilis, gonorrhea, chlamydia, genital herpes, HPV, genital warts, and hepatitis B. The law requires that an individual who is aware that they are infected with an STD must inform their partner before engaging in any sexual activity. Failure to do so can result in criminal prosecution. Additionally, individuals who negligently transmit an STD without informing their partners may face civil lawsuits for damages. It's important to note that the specifics of the law and the penalties for violations can vary, so consulting with an attorney for detailed legal advice is recommended for anyone facing such issues in Montana.