WINNIPEG, Manitoba (Reuters) - Four Canadians have been infected with the Zika virus from traveling to affected countries, government health officials said on Friday, one more than Health Minister Jane Philpott reported a day earlier.

Larvae of Aedes aegypti mosquito is seen in a research area to help prevent the spread of Zika virus and other mosquito-borne diseases, at the entomology department of the Minister of Public Health, in Guatemala City, Guatemala January 28, 2016. REUTERS/Josue Decavele

The mosquito-transmitted virus has been linked to brain damage in thousands of babies in Brazil. There is no proven vaccine or treatment.

Aedes mosquitoes that transmit the virus are found in all countries in the Americas except Canada and Chile, according to the Pan American Health Organization.

For that reason, the risk to Canadians is “very low,” although becoming infected during travel is possible, said Greg Taylor, Canada’s chief public health officer.

Two of the infected Canadians are from the province of British Columbia and one each are from Alberta and Quebec.

The virus has been linked to a devastating birth defect called microcephaly in which babies are born with abnormally small heads and brains that have not developed properly. Taylor said he was not aware of any pregnant women in Canada infected.

Some of the travel by infected Canadians was to Colombia and El Salvador, said Rebecca Gilman of the Canadian health department. Health officials did not say when they returned to Canada.

A consortium of Canadian and U.S. scientists is working on a vaccine, but those efforts do not involve Canada’s Public Health Agency.

Taylor said the agency is looking into a possible role in the project.

He said there have been a few reports suggesting the possibility that Zika can be transmitted through blood transfusions or sex. Canadian Blood Services has asked potential donors who have traveled outside of Canada, the United States and Europe to postpone donations for one month after returning.