Canada on Wednesday confirmed its first human-to-human spread of swine flu infection, as the country' s total cases rise to 19.

Three new cases were reported both in the provinces of British Columbia and Ontario, which already have cases.

All new cases are mild, but one of the patients in British Columbia has not been to Mexico recently and is believed to contract the virus from another person, said Dr. David Patrick of the provincial Center for Disease Control.

But he noted it is still unsure how easily the virus spreads. "It's still possible it will (spread easily), but the jury is still out," he noted.

Experts have warned of more cases in Canada and even deaths.

Meanwhile, Canadian scientists, who helped Mexico identify the new flu virus, is learning more about it.

Scientists at the National Microbiology Laboratory have found that the virus appears to have an incubation period of two to seven days. There is evidence it is capable of second- and third- generation infections, as the person initially infected gives the virus to a second person who then gives it to a third.

The Canadian public remain calm and the government has urged necessary precautionary measures such as washing hands frequently and avoiding contacts with people having flu symptoms.

(Xinhua News Agency April 30, 2009)