Forty-five U.S. states have made failure to do so a criminal offense. Two-thirds of HIV-positive adults are not aware of that.

"HIV criminalization is the biggest driver of stigma in our society," said Sean Strub, the HIV-positive founder of the SERO Project, a non-profit human rights organization combatting HIV-related stigma by conducting original research, briefings, forums and meetings around the country aimed at ending inappropriate criminal prosecutions of people with HIV.

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"After all," said Strub, "what is more stigmatizing than when the government enshrines criminalization in the law, making different laws for different groups of people based on an immutable characteristic" such as HIV infection? The result, he said, is the creation of "a viral underclass of persons with rights inferior to others, especially in regard to their sexual expression."

Consider Nick Rhoades, an HIV-positive gay man in Iowa, going about his life. Faithful adherence to his medications rendered Rhoades' HIV infection undetectable. Studies indicate those with undetectable virus are up to 96 percent less likely to transmit the virus to someone else. Rhoades arranged a sexual encounter with a man he met online. Neither of them spoke about HIV.

When a friend later told the other man that Rhoades was HIV-positive, the man went to the county prosecutor and pressed charges. Despite the fact that Rhoades used a condom, had an undetectable viral load, and did not transmit the virus, he was sentenced to 25 years in prison for not disclosing his HIV status. After a year, the judge reconsidered Rhoades' sentence and released him -- but still required him to register as a sex offender for the rest of his life.

"Criminalizing the sexual conduct of those living with HIV is justified only when there is evidence that an individual intended to harm another person."

HIV-specific criminal laws in about two-thirds of U.S. states mean people with HIV are potentially subject to prosecution for not disclosing their HIV status, while 45 states have specific laws about sexual relationships. Other states do not have HIV-specific statutes, but a positive person can still be prosecuted under general criminal statutes. To date, HIV-specific criminal charges have been filed more than 1,000 times in the United States alone.

These laws undermine public health efforts to identify those with HIV and get them into treatment, and thus to greatly lower their risk of infecting anyone else. A 2012 SERO Project survey of 2,076 HIV-positive Americans found that, especially in the Midwest, nearly half of respondents felt it was reasonable to avoid HIV testing -- 40 percent said the same about avoiding medical care -- because of fear of prosecution.

The survey also found that nearly two-thirds of respondents weren't aware of the laws in their states requiring (or not) HIV-positive people to disclose their status before having sex with someone. Even fewer were clear about what behaviors put them at risk for arrest in their state. Although 58.9 percent believed it was ethical or morally right to disclose their status, more than 8 in 10 respondents believed that both sexual partners share equally in the responsibility for safer sex, a view in line with the usually accepted understanding of individual responsibility and consensual sex between adults.

"Criminalizing the sexual conduct of those living with HIV is justified only when there is evidence that an individual intended to harm another person," said Strub. "Prosecutions in these instances should focus on the proof of intent to harm and the resulting injury."

Without this specificity, Strub added, laws criminalizing HIV "perpetuate the persistent public perception that those with HIV, solely by virtue of their infection with HIV, are inherently dangerous and pose a unique and significant risk to the community."