Swine flu has entered a new phase in Ontario as the virus continues to spread in some communities, a provincial health official said Thursday.

As of Wednesday, the number of reported cases in the province had jumped 25 per cent in the past three days. Since Monday, 179 cases were reported, mostly in the Greater Toronto Area, bringing the province's total to 894.

'It hasn't reached the phase six level where a large per cent of the population have it, and we're seeing doctors offices being overwhelmed with patients.'— Dr. Michael Gardam

"We need to shift from the number of cases," Dr. Michael Gardam, director of infectious diseases prevention and control at the Ontario Agency of Health Protection and Promotion, said in an interview with CBC News.

"We're in a funny phase right now, where I'm telling you that this is continuing to spread and we're measuring less, and that's normal.

"We don't need to measure anymore to know if this has spread into the community; it has. So now we're measuring in much broader terms to get a sense of how big an impact is this on the Ontario, or depending on where you are, the Canadian or the American population."

Testing everyone who has flu-like symptoms, asking about travel histories to Mexico and tracing anyone who has been in contact with a confirmed case no longer offer public health officials any valuable information.

Instead, testing for the H1N1 strain is only recommended for people who are sick enough to be hospitalized.

Since test results take a few days to get back, confirmation of H1N1 also doesn't offer any guidance to doctors deciding on how to treat patients. Rather, they base their treatment decisions on symptoms, underlying sickness and age.

Flu level 'relatively quiet'

The new measuring method relies on 80 sentinel physicians across Ontario who continue to take swabs regularly as part of regular influenza surveillance, as well as tests of patients who go to emergency room or intensive-care units with flu symptoms. Neither measure is showing an unusually high level for June, Gardam said.

"It hasn't reached the Phase 6 level where a large per cent of the population have it, and we're seeing doctors' offices being overwhelmed with patients.

"We have a number of markers that we follow that says things are 'relatively' quiet with this right now, but that is not to say this is not spreading in the general population."

Severity of illness varies

Just as with seasonal flu, some areas of the province, country and world will have worse disease than others.

As of Wednesday, the total number of cases of H1N1 in Canada was 1,795.

Quebec had the second-largest number of cases at 346 — up 37 since Monday.

Three deaths have linked to swine flu in Canada, two in Toronto and one in northern Alberta.

Public health officials in New York City have reported seven deaths in people, including six with an underlying illness that can interfere with normal breathing. One death is still under investigation.

More than half of the 1,863 new cases recorded worldwide on Wednesday by the World Health Organization were reported in the United States.

The U.S. Centers for Disease Control and Prevention said the virus has reached all the states.

Australia and the United Kingdom also had triple-digit increases, at 204 and 110 new cases, respectively.

"They're [WHO's] tallies of however many tens of thousands of cases became less and less relevant every day," said Gardam. "All of our plans say that you'll do intensive surveillance early on and then you will pull back."

WHO officials are closely watching for signs of H1N1 spreading rapidly from person to person in a region outside North America, rather than cases being brought in by travellers.

Under WHO's criteria for declaring a global outbreak or pandemic, the agency needs to see community-wide spread in a region outside of North America, where swine flu originated.

With files from The Canadian Press and The Associated Press