A bill passed by MPs in Uganda which criminalises the transmission of HIV has been criticised by the campaign group Human Rights Watch (HRW).
Those who wilfully pass on HIV could face a fine of $1,900 (£1,130) or a 10-year jail term or both.
Pregnant women and their partners will also have to be tested for HIV and it allows medical providers to disclose a patient's HIV status to others.
Such measures would seriously impede the fight against Aids, HRW said.
'Stigma and discrimination'
The government says the legislation, which President Yoweri Museveni must now sign into law within the next three months, will prevent Aids from spreading.
But in a report HRW said the bill, passed by parliamentarians on Tuesday, was a "step backward in the fight against Aids".
"It is founded on stigma and discrimination and based on approaches that have been condemned by international health agencies as ineffective and violating the rights of people living with HIV," HRW senior Africa researcher Maria Burnett said.
The criminalisation of HIV transmission, attempted transmission and behaviour that might result in transmission by those who know their HIV status is "overly broad and difficult to enforce", its report said.
HRW and other campaigning groups say that mandatory HIV testing and the disclosure of medical information without consent violate fundamental human rights.
Margaret Mungherera, president of the Uganda Medical Association, said one the biggest achievements in the country's fight against Aids had been de-stigmatising HIV.
"We have spent time telling people to channel their energies into making sure that they get tested, and if positive get treatment, and live productive lives. We have told them it's pointless to focus on who infected whom. This law is going to reverse all that," she told the BBC.
The BBC's Patience Atuhaire in the capital, Kampala, says supporters of the legislation believe it is necessary to protect women and younger girls who are put into vulnerable positions by sexual partners who do not reveal that they have Aids or are HIV-positive.
Uganda has won praise for its vigorous campaign against HIV/Aids.
This has helped to reduce the prevalence of the virus - which reached 30% of the population in the 1990s - to single-digit figures.