OTTAWA - The federal government expanded its swine-flu prevention campaign to Facebook, Twitter and YouTube as the number of confirmed cases continued to climb Friday.

Officials announced a new "citizen-readiness campaign" as the number of confirmed Canadian cases of the flu strain known as H1N1 jumped to 51 Friday with new cases in B.C., Nova Scotia, Ontario, Alberta and New Brunswick.

To date there are 15 confirmed cases in B.C., 14 in Nova Scotia, 12 in Ontario, eight in Alberta, one in Quebec and one in New Brunswick.

But in the midst of that Canadian officials were sounding hopeful.

The country's chief public health officer said there were several reasons for optimism -- namely the upcoming summer, and the extremely mild nature of the cases in Canada.

He cautioned that the virus could mutate into a more severe form, as it did in the 1918 pandemic, but that every patient in Canada is making a full recovery so far.

"What gives me short-term optimism is that we are at the end of what would normally be flu season," said David Butler-Jones, the chief public health officer.

"So the chances are that this will die down over the summer, assuming that it follows the normal pattern for influenzas, and that we will be in a position to develop a vaccine in the summer. . .

"The second piece of optimism is the cases so far in Canada and the U.S. have been more typical of seasonal -- and mild seasonal flu, not even a severe seasonal flu."

At the same time the government announced an expanded prevention campaign, which will target mainstream media and social networking sites and emphasize the importance of hand-washing, covering sneezes and staying home when sick.

He reminded people to visit www.fightflu.ca for more information.

Prime Minister Stephen Harper said he's confident that Canadians, while taking the necessary precautions and eyeing developments with a sense of concern, are not getting carried away.

"My sense is the public is, like ourselves, concerned, but I don't sense a panic," he said in Edgeley, Sask.

"I sense the public is listening very carefully to various advisories and warnings they are getting and responding appropriately and that's what we encourage."

Harper was asked about the World Health Organization's decision Thursday to begin referring to the virus by its formal name rather than the more colloquial "swine flu."

"This is obviously a medical condition so it makes sense to refer to it that way and I gather that's a standard that the World Health Organization is now trying to encourage," Harper said.

"The health risks here are to humans; that's the concern ... It is not the health of the hog industry in any way that is at stake here, so we will encourage that terminology."

B.C.'s four new cases involved one youngster, one teenager and two adults -- all in the province's Lower Mainland, all mild and all involving people who were either recently in Mexico or in contact with people who were, said Premier Gordon Campbell.

While neither the status nor the number of cases in Canada should be considered cause for alarm, the level of worry surrounding a virus that's fuelling fears of a global pandemic is perfectly justified, Campbell told a news conference.

"Unfortunately, we may see some deaths. We have deaths from flu every year. It's important for us to recognize that," he said.

Much the same warning came from health officials in Nova Scotia, which is where Canada's first cases of H1N1 came to light last weekend, all of them from a private school where a group of students had recently returned from a school trip to Mexico.

All the new cases are students from the King's Edgehill private school in Windsor, N.S., said Dr. Robert Strang, Nova Scotia's chief public health officer.

"At this point we're not seeing severe cases such as have been experienced in Mexico," Strang said. The province's total caseload is now 14, he added.

"We do expect to see new cases and we anticipate more in the coming days. As with normal flu, once the number of cases does increase, it is normal to see more severe cases and potentially even some deaths."

Ontario reported four more mild cases, all in the Toronto area, bringing the province's total to 12.

In Alberta, two more mild cases involving two women from Calgary, one a recent returnee from Mexico and the other from Tennessee, brought the total number in the province to eight, said Dr. Andre Corriveau, the province's chief medical officer of health.

Corriveau said health officials have heard that some businesses in Alberta are requiring any staff who have recently visited Mexico to see a doctor before they return to work, a step he described as unnecessary.

"We are appealing to people to be reasonable -- not to clog our health-care system unnecessarily."

On Friday, the Catholic Archdiocese of Edmonton said it was asking parishes to make changes to help prevent the spread of infection.

Priests have been asked to stop distributing consecrated wine from the common cup and to encourage parishioners who usually receive communion wafers on their tongue to receive it in their hands instead.

An official with the Canadian Conference of Catholic Bishops said it was not immediately clear how many of the other 14 Archdiocese across the country are taking similar measures.

Strang said all of the Nova Scotia students who had swine flu were now better, after spending at least seven days in isolation, and are no longer infectious.