A sex worker checks her smartphone as she and others wait for customers in a brothel at Dolly prostitution complex in Surabaya, Indonesia. (Dita Alangkara/AP)

The decriminalization of sex work could significantly decrease global HIV infections among female sex workers, leading to a reduction of at least a third in three countries examined by researchers, according to a new study.

In a paper presented Tuesday morning at the 20th International AIDS Conference in Melbourne, Australia, researchers who studied HIV among female sex workers in Canada, India and Kenya concluded that infections could be reduced by 33 to 46 percent in those countries.

“Across all settings, decriminalization of sex work could have the largest impact on the HIV epidemic among sex workers over just 10 years,” said Kate Shannon, an associate professor of medicine at the University of British Columbia and the lead author of the study. “Governments and policymakers can no longer ignore the evidence.”

The study was the first in a series of papers by the Lancet to be presented at the global conference. The studies urge that any efforts to address the HIV epidemic put the challenges faced by sex workers at the forefront.

Five high-risk groups — men who have sex with men, transgender people, people who inject drugs, prisoners, and sex workers — account for about half of all new HIV infections worldwide, the World Health Organization reported this month. Female sex workers are 14 times as likely to have HIV as other women, according to WHO, with transgender women almost 50 times as likely to have HIV as other adults.

Sex workers and the spread of HIV The infographic addresses misconceptions.

The study, written by Shannon and her colleagues, found that high rates of violence, police harassment and poor working conditions, combined with poor access to prevention and care significantly increase HIV risks for sex workers.

Anna-Louise Crago, a doctoral candidate at the University of Toronto, was an editor of the Lancet series. As a former sex worker in Canada, Crago has a firsthand understanding of the challenges faced by this population.

“We’ve long reported that criminalization impedes our ability to protect against HIV,” she said.

Making sex work a crime pushes sex workers to find isolated areas, increasing risk of violence, and due to fear of arrest, transactions are rushed, and sex workers are less likely to insist on limits and safeguards, including condom use, the study finds.

Many sex workers quoted in the study report police confiscating, destroying and using condoms as evidence. Sex workers often stop carrying condoms for fear of arrest.

“Use of condoms as evidence is one glaring example of how criminalization of sex work affects public health,” said Sienna Baskin, spokeswoman for the Sex Workers Project in New York.

Because of their criminal status, sex workers tell Baskin they fear that disclosure of their work will leave them stigmatized by health providers and in danger of losing custody of their children.

“Criminalization can have a direct impact on access to health care. Treatment, such as anti­retroviral therapy, requires stability and consistency. Being at risk for criminalization disrupts this,” said Baskin.

In Kenya, according to the data in the study, even modest scale-up of sex-worker-led outreach could prevent a quarter of new infections among sex workers.

One sex worker in the Kenya case study said that when she went to a health center and the doctors realized she was a sex worker, they did not treat her like a human being, and she left without treatment.

In India, the study shows progress reducing HIV risks has been made through sex-worker-led efforts to address stigma and empower the community.

“We see from the evidence across settings that sex-worker-led efforts must go hand in hand with structural change,” said Shannon.

“Human Rights Watch has found that criminalization drives sex workers away from health services in numerous ways, from police using condoms as evidence of prostitution [in the United States and Cambodia] to fear of arrest at drug treatment centers and harm-reduction sites [Thailand] to an inability to complain to police about rape,assault from clients [U.S., Cambodia, China],” said Megan McLemore, a senior researcher with the group’s health and human rights division. The organization supports the call for decriminalization of adult, consensual sex work “as evidence mounts that not only does criminalization undermine sex-worker health but that the reverse is true.”

In New South Wales, Australia, where sex work has been decriminalized since 2009, sex workers have a lower HIV prevalence than the general population, added McLemore.

In December, Canada’s Supreme Court struck down laws targeting sex work, and the Canadian government could decriminalize the activity this year.