Officials say a traveller from Alberta is one of three Canadians to have contracted the Zika virus while overseas.

U of A Professor of Medicine and Public Health Stan Houston told CTV News a traveller from Calgary recently returned home with the Zika virus. Officials say the other two cases are in B.C.

“These are returned travellers, so far there haven’t been people actually getting it, transmission occurring in the [United] States for example. But that could happen,” Houston said.

Officials say three Canadians have been confirmed to have the virus, which is transmitted by a certain species of daytime mosquito, and has spread to more than 20 countries in the Americas in the last year, in addition to French Polynesia.

The virus has been linked to a sudden increase in microcephaly, a condition where babies are born with abnormally small heads – a spike in the number of babies born in Brazil with the condition has been reported.

To combat this, authorities in some countries directly affected by Zika virus are advising women to hold off getting pregnant, and pregnant women are being advised to not travel to any of those countries.

Houston told CTV News that women travelling abroad who are thinking of getting pregnant should wait about three months after returning to Canada.

Two major Canadian airlines have put policies in place to respond to advisories surrounding Zika virus – Air Canada has announced moms-to-be can change their flights or receive a refund, if they provide a doctor’s note, and Westjet says guests can also change their flight or get a travel credit.

Zika has also been linked to Guillain-Barre syndrome, a condition where the body’s immune system attacks the nervous system.

The virus has been on the radar for decades, but has only recently spread to almost every country in the western hemisphere, except for Chile and Canada.

The World Health Organization held an emergency meeting on the subject, and warned the virus could spread to as many as 4 million people by next year.

“It is now spreading explosively,” Director-General of the WHO Dr. Margaret Chan said. “As of today, cases have been reported in 23 countries and territories in the region.

“The level of alarm is extremely high.”

In Canada, Canadian Blood Services says they are monitoring the situation, and looking into revisions to travel policies to protect the blood supply from the threat of the virus.

“If you have been travelling in endemic areas where Zika virus is present, we’re going to ask you not to come in and donate right away after travelling,” Dana Devine with Canadian Blood Services said in an interview in Ottawa.

Health officials say one in five people who contract the virus will notice symptoms, if they are not pregnant.

Symptoms resemble a mild illness, with fever, rash, joint pain or red eyes.

With files from CTV News and Carmen Leibel