Yes — in most of the United States, it is illegal to knowingly spread an STD, and in many states it is illegal even to expose someone without actually transmitting the infection. Roughly 32 states have HIV-specific criminal statutes, others use general communicable-disease laws, and prosecutors everywhere else can reach for assault, battery, or reckless-endangerment charges. On top of criminal exposure, an infected person who stays silent can be sued for money damages by the partner who got sick.
How the Criminal Law Reaches STD Transmission
States use three different tools. The first is an HIV-specific or STD-specific statute that makes it a standalone crime to expose or infect someone while knowing your diagnosis. The second is a general communicable-disease law in the state health code covering any infectious condition. The third is an ordinary criminal charge — assault, aggravated assault, battery, or reckless endangerment — where the transmission is treated as the harmful act. In some jurisdictions, HIV in particular has been characterized as a deadly weapon for purposes of aggravated assault.
Which tool the prosecutor picks changes what has to be proved. Under a specific statute, the government usually just needs to show you knew your status and did the prohibited thing. Under an assault theory, the state has to prove the standard elements of assault, including bodily injury or imminent danger.
Exposure Can Be Enough
A common misconception is that your partner must actually get sick before you can be charged. Many states criminalize exposure alone. If you know you have HIV and have unprotected sex without disclosing, you can be prosecuted even if your partner never seroconverts. Other states require proof of actual transmission, which makes charges harder to bring but tends to carry heavier penalties when they stick. Where exposure alone is the offense, grading often drops to a lower-level felony or misdemeanor.
What the Prosecution Has to Prove
Knowledge is the linchpin. At a minimum, the government must show you knew you were infected before the encounter. For most statutes, that is the entire mental state. A smaller group of states demand specific intent to transmit — not just awareness of your status, but a desire to pass the infection on.
Proving knowledge almost always starts with medical records. A lab result dated before the sexual contact, prescriptions for antiretrovirals or antibiotics, and provider notes carry decisive weight. Text messages and dating-app exchanges in which someone acknowledges a diagnosis, mentions medication, or dodges a direct question about testing have carried cases on their own. Prior partners and healthcare providers can also testify to what the defendant knew.
Specific intent is a much higher bar. Prosecutors in those states need evidence that the person wanted to spread the infection: statements to that effect, a pattern of targeting uninformed partners, or deliberate refusal of treatment.
Penalties
Sentences range from a few months in county jail to a decade or more in state prison. Among states with HIV-specific laws, most classify the offense as a felony; a smaller number treat it as a misdemeanor, and some use tiered schemes keyed to whether transmission actually occurred.
Collateral consequences can outlast the sentence. A handful of states have required sex-offender registration for people convicted under HIV-specific statutes, though reform advocates have successfully challenged or repealed that requirement in several states over the past decade. Probation can carry mandatory testing, treatment-compliance checks, and partner-notification conditions.
You Can Also Be Sued
Criminal charges are not the only risk. Someone who contracts an STD from a partner who knew and said nothing can bring a civil lawsuit for money damages. These cases usually rest on battery (harmful or offensive contact without consent), negligence (failing to take reasonable care to prevent transmission), or intentional infliction of emotional distress. The standard of proof is lower than in a criminal case: more likely than not, rather than beyond a reasonable doubt.
Damages can be substantial. Plaintiffs recover for medical treatment, ongoing medication costs, lost income, pain and suffering, and emotional distress. Punitive damages are available where the conduct was especially reckless or malicious. Verdicts and arbitration awards in these cases have reached into the millions, though outcomes depend heavily on the disease, the evidence, and the state.
Timing surprises many people. STDs like HPV and herpes can stay dormant or undiagnosed for years. In most states, the statute of limitations does not start running on the date of sex. Under the discovery rule, the clock begins when you knew or reasonably should have known that you were infected and that a particular person’s conduct likely caused it. If you were diagnosed years after the exposure, you probably still have time, but you should not wait once you connect the dots.
Defenses
The strongest defense in most jurisdictions is simple: you told your partner and they chose to go ahead. Informed consent is a complete defense under many statutes and a powerful one even where it is not written into the law. Texts, witness testimony, or the partner’s own admissions showing that you disclosed will usually end a criminal case.
In states that have modernized their laws, taking precautions can also defeat a charge. Using a condom or maintaining an undetectable viral load through consistent treatment may qualify as an affirmative defense. In older-framework states these facts are not formal defenses, but they often influence charging decisions and sentencing.
Lack of knowledge is the most basic defense. If you genuinely did not know you were infected, you cannot be convicted under any statute that requires knowledge. That is why medical records and testing history sit at the center of these cases. Courts generally do not accept willful ignorance, though — if a test was done and results were communicated through normal channels, you are typically treated as having known.
In civil cases, defendants sometimes argue the plaintiff assumed the risk by failing to ask about health status. In most states that argument has been folded into comparative-negligence analysis: it reduces the plaintiff’s recovery rather than eliminating it. Courts have been reluctant to let that excuse a defendant who actively concealed an infection.
The Duty to Disclose
Separate from any criminal statute, many jurisdictions recognize a legal duty to disclose an STD to a sexual partner, grounded in the broader obligation not to cause foreseeable harm. Where specific disclosure statutes exist, they usually require a person who knows they are infected to inform any partner before contact. HIV is the most commonly covered disease, but some laws extend to other incurable or highly transmissible infections.
What counts as adequate disclosure is less settled than you might expect. Mentioning a diagnosis in passing may not satisfy the standard if the other person did not understand the implications or was not given a real chance to decline. Written acknowledgment is not legally required in most places, but it is far stronger evidence than a verbal exchange one party may later deny.
Treatment advances have complicated these duties. A person with an undetectable viral load has effectively no risk of sexually transmitting HIV, and some courts and legislatures have started to factor that in. Many older statutes still make no distinction between someone on effective treatment and someone untreated. Until a state updates its law, the safest course remains disclosure before any sexual contact, regardless of treatment status.
Why the Rules Vary So Much
A number of states have reformed or repealed their HIV-specific criminal laws since 2014. At least five have fully repealed statutes that criminalized HIV alone, and more than a dozen others have modernized their laws. The CDC has publicly said that current scientific and medical evidence should inform these statutes and that states should consider updating or repealing outdated ones.1Centers for Disease Control and Prevention. HIV Criminalization and Ending the HIV Epidemic in the U.S.
Reforms tend to cluster around three ideas: requiring specific intent to transmit rather than mere knowledge, demanding that the conduct involve a scientifically substantial risk of transmission, and adding affirmative defenses for disclosure with consent, condom use, or an undetectable viral load. At the federal level, the REPEAL HIV Discrimination Act has been introduced in Congress to prompt a national review, but it has not been enacted.2Congress.gov. H.R. 1305 REPEAL HIV Discrimination Act of 2021 The driving concern is that laws written in the 1980s and 1990s no longer match what medicine knows about transmission risk.
Public Health Reporting Is a Separate Track
Criminal and civil liability aside, public health law creates its own layer. Healthcare providers in every state must report certain STD diagnoses — syphilis, gonorrhea, chlamydia, chancroid, and HIV are reportable nationwide — to state or local health departments.3Centers for Disease Control and Prevention. Sexually Transmitted Infections Treatment Guidelines, 2021 – Reporting and Confidentiality Health departments then handle partner notification and contact tracing. The diagnosed person’s identity is kept confidential; a notified partner learns of possible exposure but not who reported it.4Centers for Disease Control and Prevention. Duty to Warn for Health Care Settings This process is administrative, not criminal — a health department contact does not mean you have been charged with anything.
If you have been diagnosed with an STD, the short version is this: find out what your state’s law requires, disclose before sexual contact, and keep evidence that you did. If you believe someone knowingly infected you, preserve messages and testing records now, because both a criminal complaint and a civil suit will rise or fall on what the other person knew and when.