TORONTO -- Canada has virtually eliminated the incidence of mothers passing HIV to their infants at birth, primarily because of high rates of pre-natal testing and ready access to drug treatment that subdues the infection, researchers say.

In 2014, there was only one case of mother-to-child HIV transmission in Canada, continuing a decade-long downward trend, said Dr. Jason Brophy, chair of the Canadian Pediatric and Perinatal AIDS Research Group (CPARG), which has been tracking cases since 1990.

"The World Health Organization definition of elimination is less than two per cent transmission, and that's where we are right now," said Brophy, an infectious disease specialist at the Children's Hospital of Eastern Ontario in Ottawa.

The finding was among data from three studies by CPARG's perinatal HIV surveillance program presented Wednesday at the 8th International AIDS Society conference on HIV Pathogenesis, Treatment and Prevention in Vancouver.

Each year, an average of about 200 babies are born in Canada to women diagnosed with HIV, said Brophy, noting that in the 1990s, before the advent of antiretroviral drugs, 84% of HIV-positive moms-to-be were diagnosed after they got pregnant.

"Whereas in the more-recent era, like 2008 to 2013, only 10 per cent were diagnosed during their pregnancy," he said, with 90% knowing they had HIV before becoming pregnant and already on infection-dampening drug treatment.

"And what that means is women are getting diagnosed and put on treatment ... and then choosing to have babies."

Antiretroviral drugs stop HIV from replicating in the cells and eventually destroying the immune system and progressing to AIDS.

But even among women who learn they are HIV-positive during their pregnancy, babies are rarely at risk of getting the infection, as long as the mothers are able to get on antiretrovirals for at least a month before giving birth, Brophy said.

"I reassure moms that for women who've been on medication and are well-suppressed and everything goes fine at delivery ... I tell them: 'Don't worry about your baby, your baby will be fine.

"I've seen hundreds of babies at this point and none have been infected. It's only the babies where mom's virus isn't suppressed at delivery -- because of not enough time on treatment or not knowing the diagnosis -- where there's a real risk of transmission."

Brophy also presented a study Wednesday that looked at the countries of origin of HIV-positive women who gave birth in Canada between 1990 and 2013. Of almost 3,900 women, 54% were foreign-born, and of those, 71% emigrated from Africa.

In the first half of the 1990s -- before the use of antiretroviral drugs -- the largest group of HIV-positive mothers came from French-speaking Haiti, with many of them settling in Quebec.

Since 2008, the largest group of HIV-infected mothers has come to Canada from Ethiopia, Congo, Zimbabwe and Nigeria.

"The interesting pattern we see in this is the source countries over time really reflect what's going on in the world around us," said Brophy. "There are many countries of conflict and we get an uptick in the number of women from those countries as people flee.