Should patients treated for HIV inform sexual partners even if the odds of transmitting the disease are very low? Morally, the answer is yes. Legally, the answer is in flux.
Canada's highest court will determine what justifies "significant risk" in the case of Clato Mabior, now serving time in a Manitoba jail. He was on antiretroviral drugs and sometimes used condoms but did not disclose his illness to sexual partners.
Originally convicted of six counts of aggravated assault and sentenced to 14 years in prison, four of Mr. Mabior's convictions were overturned last year. The Manitoba Court of Appeal found not everyone who had sexual relations with him was exposed to "significant risk." The Crown appealed to the Supreme Court.
Up until now, the courts have relied on a 1997 Supreme Court of Canada ruling that stated HIV-positive patients can be prosecuted if they haven't disclosed their illness and exposed their partner to "significant risk" during sex. Over the past 14 years, the science and treatment of HIV has changed.
When it comes to transmitting HIV, estimating risk is a moving target often discussed in ranges by scientists. Those estimates do not take into account imperfect behaviour such as drunkenness, sloppy condom use, missed antiretroviral medication and hazards of casual sex with multiple partners.
Estimates of transmission when using a condom range from 1 in 2,000 to 1 in 10,000. So far, no comprehensive statement has been made about the impact of low viral loads and HIV infection during unprotected sex. The risk is never zero.
Science is not perfect. And the test for a viral load - which refers to the number of copies of the virus in a millilitre of body fluid - is simply a medical snapshot. A forgotten dose of medication, a common infection or sexually transmitted disease can all alter a patient's viral load. An HIV patient can develop viral resistance.
Scientific advancements have transformed HIV/AIDS from a killer disease into a chronic one but ultimately this is a case about consent.
All but one of the women who had sexual relations with Mr. Mabior said they would not have consented to sex if they knew his disease status. Surely, they deserve the right to choose whether they risk developing disease that may devastate, even kill them.