The woman is believed to have contracted the virus after having sex with a male partner, who was diagnosed after visiting a country affected by the Zika epidemic, according to Dr. Gregory Taylor, Canada’s chief public health officer. Both diagnoses were confirmed through antibody tests conducted by the Public Health Agency of Canada, he said.
Taylor emphasized that Zika’s risk to the Canadian public is low — and he is not surprised to see the country’s first sexually-transmitted case.
Since emerging in Brazil last year, Zika has spread to 42 countries, primarily in Latin America and the Caribbean, and eight countries have already confirmed sexually-transmitted cases.
“Evidence is suggesting that the virus can live in semen or be present in the semen for a long time, at least two months,” Taylor said. “There are now 5.5 million Canadians travelling to these countries every year, this is a huge number of people . . . so we expected to see a (sexually-transmitted) case.”
The Zika virus was first discovered in 1947 and was once thought to only cause mild disease.
It is believed to be primarily spread by the Aedes aegypti mosquito, which is not found in Canada.
But the current epidemic has proven Zika’s true and dangerous potential, and there is now scientific consensus that the virus can cause serious neurological problems, including birth defects and Guillain-Barré syndrome, which can cause temporary but life-threatening paralysis.
Public health officials are also realizing that sexual transmission of Zika likely occurs more often than previously assumed. The first known case was reported in 2011, when the journal Emerging Infectious Diseases published a case report of a scientist who contracted Zika in Senegal and transmitted the virus to his wife after returning home to Colorado.
But that case was mostly treated as a curious oddity and public health officials did not seriously consider that Zika could be sexually transmitted until the current epidemic.
Since 2015, Zika infections likely acquired through sex have been reported in Argentina, Chile, France, Italy, New Zealand, Peru, Portugal and the United States of America.
Earlier this month, the U.S. Centers for Disease Control and Infection also reported that a Texan man who visited Venezuela in January had infected his male partner with Zika through anal sex.
In Canada, the Public Health Agency of Canada has now tested more than 3,400 suspected Zika cases.
In addition to this latest case, 55 people have tested positive, including four pregnant women — all of whom acquired the virus overseas. (The Ontario Ministry of Health and Long-term Care would not say whether the person at the centre of this latest case is pregnant, and cited patient confidentiality as the reason.)
Given the size of the Zika epidemic, and the number of Canadians who travel to affected countries, it’s surprising that Canada is only now reporting its first sexually-transmitted case, said Dr. Doug Sider, medical director of communicable diseases with Public Health Ontario.
He said getting Zika from sex is probably still a rare event, but much more research is needed to better understand this method of transmission.
“How big of a reality is it going to be? Can there be female-to-male transmission? Can there be asymptomatic transmission, especially from male to female?” Sider asked.
“These are all the things that need to be further worked on.”
What to do about Zika
Worried about sexually-transmitted Zika or getting pregnant after travelling to an affected country?
Here’s the latest advice from public health officials:
Women: If you are planning to get pregnant, and may have been exposed to Zika, it is “strongly recommended” that you wait at least two months before trying to conceive.
Men: If you’ve travelled to a Zika-affected country and have s3x with men or women, you should use cond0ms for six months. If you have a pregnant partner, then it is strongly advised that you use cond0ms for the duration of the pregnancy and, if you’re trying to conceive, wait at least six months, as the virus can linger in semen.
—with files from Evelyn Kwong