Ottawa-The impact of the Zika virus on infected Canadian travellers was “more severe” than expected, say researchers. A new study looked at Canadians returning from trips to Zika-affected regions who sought treatment at a national network of travel clinics.

Researchers examined 1,118 patients who visited one of those clinics over a year. They say they found a higher rate of complicated illness than anticipated in Zika patients.

The research was published on Monday in the the Canadian Medical Association Journal and the doctors behind the limited study say it underscores the importance of prevention. The Canadian patients in the study visited one of seven travel clinics.