Since testing began in B.C. last November, 635 Zika virus tests have been conducted. But only in the last few days has the most dreaded scenario occurred: positive tests in pregnant women whose fetuses may develop birth defects.
Each of the seven cases involved travellers who returned from these Caribbean, Central and South America places: Colombia, El Salvador, Haiti, Dominica and St. Martin.
Five of the B.C. residents who have tested positive are women. None of the British Columbians who have been infected have been ill enough to be hospitalized. Indeed, in up to 80 per cent of infections, there are few symptoms.
According to the latest update from the federal government (April 14), there have been 46 travel-related cases of Zika in Canada. Another update is due in a few days.
There is a proven association between Zika virus infection and babies born with microcephaly (abnormally small heads) and other abnormalities that can limit children’s growth, mental and physical abilities.
Dr. David Patrick, an expert in epidemiology and public health at the University of B.C. and B.C. Centre for Disease Control (BCCDC), said in an interview that pregnant, infected women will receive repeat ultrasounds (every three to four weeks) at the hospital to monitor fetal head measurements and other developmental cues.
“Unfortunately, ultrasound cannot reliably detect microcephaly until late in the second trimester and there is no gestational age by which microcephaly can be ruled out.”
Dr. Julie van Schalkwyk, head of obstetrics and gynecology at B.C. Women’s Hospital, refused to speak about the two cases being monitored at the hospital. But she said it is an anxiety-provoking issue that keeps her up at night since so little is known about the virus. Doctors don’t know how the virus will affect pregnant women, how likely it is it will infect the fetus, the likelihood of birth defects if the fetus is infected, which stage in development the infection may cause the most harm to fetuses and if sexual transmission poses a different risk of birth defects than mosquito-borne transmission.
“It’s a terrible state for us to be in because we have so little information to give patients about the likelihood of their babies becoming infected, and if they do, how this will manifest itself in fetal abnormalities. It really is like being blindfolded,” said van Schalkwyk, who is also a specialist in infectious diseases during pregnancy.
“It’s a very distressing situation for doctors and their patients. I don’t know if there’s any analogy in (maternal-fetal) medicine.”
Infected, pregnant women can choose to have an abortion up to 23 weeks plus six days gestation. Pregnant women do not have to have any symptoms of Zika to get tested; they must merely demonstrate they were in an area where they might have been exposed to the virus.
B.C. experts say women who are pregnant or trying to get pregnant should think about postponing travel to areas where Zika is circulating. The Public Health Agency of Canada recommends that women coming back from such areas should delay getting pregnant for at least two months. And since Zika can persist in semen for more than two months, abstinence from intercourse or strict adherence to proper use of condoms for several months is advised by experts.
Manitoba public health officials recently recommended condoms or abstinence for at least six months among men who have travelled to an area of risk, who have symptoms of the virus or are diagnosed with it.
Public health experts recommend infected men with partners who are pregnant or may become pregnant use condoms throughout the duration of pregnancy.
“If you want to play it 100-per-cent safe, wait a few months (after travel) before conceiving because the virus can hang around in the body, in semen, for example,” Patrick said.
Patrick said doctors can refer travellers returning from Zika-transmission areas to laboratories for blood and urine collection if they have two or more symptoms within two weeks of their return. Samples are then tested at the BCCDC lab.
In the winter months, when so many B.C. residents were travelling south to sunnier locations, as many as 80 tests were being carried out per week in this province. That number has now tapered off to about 30 a week. Patrick said the trends so far show that women are four times more likely to get tested because of pregnancy concerns.
“We’ve seen no evidence to this point that women are more susceptible (to getting infected),” he said, adding that early signs are that pregnant women who have no symptoms appear to have a lower risk of having babies with congenital defects.
While many thousands of people in countries like Brazil have already been infected, and such people develop immunity for an undetermined duration, as Patrick points out, “Zika is still going to be around for a long time,” so endemic countries can’t let up on mosquito control efforts, nor should travellers when it comes to avoiding mosquito bites.