The transmission of a sexually transmitted disease (STD) from a person who knows or should know they have the disease to another person who is not informed of that fact before engaging in sexual contact with the infected person may result in both civil liability (for money damages) and criminal liability (for penalties).

Laws vary from state to state and some states have both civil and criminal statutes (laws enacted by the state legislature) that specifically address the transmission of sexually transmitted diseases. In other states civil lawsuits may be filed and criminal prosecutions may be made under traditional legal theories such as negligence in a civil lawsuit and battery (harmful or offensive physical contact without consent) in a criminal prosecution.

In Missouri, the transmission of a sexually transmitted disease (STD) by an individual who knows or should have known about their infection to an uninformed partner can lead to both civil and criminal consequences. Under Missouri law, it is a criminal offense for someone with HIV to knowingly expose another person to the virus without their consent. This is outlined in Missouri Revised Statutes Section 191.677, which makes it a felony to act in such a manner. Additionally, individuals who transmit other STDs may face criminal charges under general criminal statutes such as assault. On the civil side, a person who is infected by an STD due to another's negligence or intentional act may seek damages through a personal injury lawsuit. The legal theories of negligence, battery, or intentional infliction of emotional distress could be applicable, depending on the circumstances of the transmission. It is important for individuals in Missouri to be aware of these laws and to seek legal counsel from an attorney if they are involved in a situation related to the transmission of an STD.