The number of confirmed swine flu cases in Nunavut more than doubled from 25 to 53 on Tuesday, with six people in hospital as a result of the H1N1 influenza virus.

Health officials in Nunavut say the jump in cases is the result of heightened surveillance since swine flu was first confirmed in the territory on May 28.

Twenty-eight new cases have been lab-confirmed since Monday, when 19 new cases of swine flu were reported. The number of hospitalized cases has also risen by one since Monday.

All the new cases are in the Kivalliq and Kitikmeot regions, which are in the central and western parts of the territory. The Health Department has not identified any of the patients or which communities they are from, citing privacy.

Chief medical officer Dr. Isaac Sobol said in all cases the patients, including those in hospital, are recovering from the illness, and stressed that there's no need to panic about the rising number.

Since the first case was reported, health-care workers across Nunavut have been testing every patient with flu-like symptoms for the H1N1 virus. Health officials said they plan to continue enhanced surveillance until June 15.

WHO concerned with Inuit cases

The spike in cases in Nunavut, which has a mostly Inuit population, has become a worry for the World Health Organization, a top health official said Tuesday.

Keiji Fukuda, WHO's acting assistant director general, told reporters in Geneva that certain populations — such as the Inuit — have been especially affected by past pandemics.

"We do know … in past pandemics that Inuit populations were very severely hit in some of the earlier pandemics and so, again, this is why these reports raise such concern to us," Fukuda said.

He noted, however, it's not clear what factors may be causing more severe cases of swine flu in northern and aboriginal communities. Possibilities include genetics, poverty and underlying chronic diseases.

"We know, for example, in the Inuit populations that some of the background levels of chronic diseases can be higher. These have occurred in villages which are relatively isolated, although, you know, there are good health-care services available.

"So I think at this time, we can say right now that we know, for example, a larger number than expected of young Inuit people did develop serious illnesses and had to get hospitalized," Fukuda said.

"I don't think we know whether this reflects one characteristic … whether it reflects socio-economic factors, whether it reflects genetic factors, whether it reflects chronic underlying diseases. I think this is not possible to say at this time."

Nunavut has a population of about 29,500, about 85 per cent of which is Inuit.

Fewer cases in N.W.T., Yukon

Compared to Nunavut's total of 53 swine flu cases, the Yukon has confirmed one H1N1 case to date, while the Northwest Territories have two cases.

In Yellowknife, potential N.W.T. cases are being treated at Stanton Territorial Hospital, where officials say one patient with the virus is being treated. Two other cases await test results.

"Most of what we're seeing are fairly mild [cases], and what we're admitting is mainly children — in fact, mainly infants under a year," hospital CEO Kay Lewis told CBC News.

"At this point in time they require oxygen [but] they're recovering quite quickly and most of them have been discharged."

In an effort to curb the spread of the H1N1 virus, the hospital has closed its children's ward to visitors beyond immediate family members.