The global medical community is scrambling to make sense of the rapid spread of the Zika virus, with the head of the World Health Organization asking the "best brains in the world" to help, while in Canada, blood donations will soon be halted for travellers returning from affected regions.
An emergency meeting of experts is planned for Monday in Geneva, called by WHO director-general Margaret Chan, who says the mosquito-borne disease is now "spreading explosively" throughout the Americas, with cases in 23 countries. Canada is expected to attend the meeting.
The link between the virus and birth defects and neurological problems, while not yet proven, has escalated the risks associated with Zika "from a mild threat to one of alarming proportions," Dr. Chan said.
Experts estimate cases could soar to between three million and four million over the coming year, and they expect the disease to spread to all countries in the Americas except for Canada and parts of Chili, the only regions where the Aedes mosquito is not found.
"I don't want to increase your anxiety, but we do expect there to be a significant outbreak of the Zika virus," Carissa Etienne, director of the Pan American Health Organization, told a special session of the WHO executive board Thursday in Geneva.
In response to the growing threat, the agency responsible for managing the blood system in most of Canada said Thursday it will announce new restrictions on donors next week.
Dana Devine, chief medical and scientific officer for Canadian Blood Services, said the agency expects to refuse donations from individuals who have travelled to countries affected by the Zika virus for "a number of weeks" after their return. The exact time is still being determined, she said, in consultation with Health Canada and Héma-Québec, which manages blood services in that province.
"We think it is the wise thing to do," Dr. Devine said, describing the chances of getting the Zika virus from blood as "really pretty tough, but not impossible."
So far, three cases of travel-related Zika virus have been found in Canada – two in B.C. and one in Alberta.
The Public Health Agency of Canada is constantly monitoring the situation, and front-line health workers are being told to be on the lookout for people who may exhibit symptoms, federal Health Minister Jane Philpott said.
"We're in communication with all stakeholders, including health-care providers, to make sure that people are aware of the appropriate symptoms that might put in mind a possible diagnosis of Zika virus and that people are tested appropriately for that," she said.
A vaccine for the virus, in development by Canadian and U.S. scientists, could be available for emergency use before the end of the year, possibly making it the first, one of the lead scientists said on Thursday.
The consortium working on the vaccine includes Quebec's Laval University, led by Gary Kobinger, the University of Pennsylvania, led by scientist David Weiner, Inovio Pharmaceuticals Inc. and South Korea's GeneOne Life Science, Dr. Kobinger said.
He hopes to start trials by September to test its safety on humans, pending regulator approval. It could be ready for emergency use a month later.
Ross Upshur, a professor of public health at the University of Toronto who studies infectious disease outbreaks, said WHO's response is in part a reaction to criticisms of its handling of the Ebola crisis in 2014-15.
An opinion piece published this week in the Journal of the American Medical Association criticized WHO for "not taking a leadership role in the Zika pandemic," given the virus's spread and the "fresh urgency as the 2016 Olympics in Rio de Janeiro loom." The article recommended WHO call an emergency meeting of experts – the very thing it did Thursday.
Dr. Upshur said the emergency meeting is an appropriate response, but the next priority must be for public health officials to nail down who is at risk, the magnitude of that risk and whether a link exists between the Zika virus and microcephaly, a rare birth defect that causes infants to be born with small heads and underdeveloped brains. A spike in cases has set off alarm bells in Brazil.
As widespread outbreaks become more prevalent, he said, public health officials must learn to respond in a professional manner.
"The idea that we are going to be seeing new viral and bacterial infectious diseases ought not to take us by surprise," Dr. Upshur said. "This is something that is happening with regularity and we need to have a system that just knows how to manage it without everybody going into panic mode."
Michael Libman, director of McGill Univeristy's J.D. MacLean Centre for Tropical Diseases, said a priority also must be the development of a good diagnostic test for Zika. No commercial test exists and there is a small window of several days when the virus can be detected. After that, the tests for antibodies is more complex and can produce false results.
The Public Health Agency of Canada's national lab in Winnipeg is the only site that can currently test for Zika. It is relying on the U.S. Centers for Disease Control and Prevention to test for antibodies to the virus at this time, but is developing this ability, the agency said in a statement.
Earlier this month, the agency issued a travel advisory, indicating pregnant women and those considering becoming pregnant may want to postpone travel to countries with the Zika virus.
With a report from The Canadian Press and Reuters