A pre-teen girl believed to have had the H1N1 virus — but no pre-existing medical condition — died on Saturday at CHEO.

The girl, who was from the Cornwall region, was initially admitted to CHEO with mild symptoms, but her condition quickly worsened.

Dr. Paul Roumeliotis, medical officer of health for the Eastern Ontario Health Unit (EOHU), said the girl was healthy until the appearance of the flu symptoms, which included fever, muscle pain and coughing.

He told the Sun the girl — whose identity has not been released — didn't appear to have an existing medical condition that could have contributed to her death.

"She had the symptoms for a couple days, then they got worse very quickly," Roumeliotis said. "That seems to be a hallmark of H1N1."

Testing to confirm it was H1N1 is ongoing.

"The preliminary test showed positive for influenza A," Roumeliotis said. "To date, all recent cases of influenza A have been identified as H1N1.

"Most of the people who get the virus get better, but for some the infection overwhelms them," Roumeliotis said. "Every year hundreds die of the seasonal flu."

Roumeliotis expressed sympathy to the family and friends of the girl.

"It is extremely sad to see the virus claim the life of a child," he said.

Her death comes at a time when 26 schools in the EOHU's catchment area have been hit with a swine flu outbreak.

Roumeliotis said an outbreak is declared when more than 10% of a school's students are absent with flu symptoms.

CHEO spokeswoman Ann Fuller said the hospital's ER is busy with new patients and a large number are showing swine flu symptoms.

"Total visits to the ER are 24% higher than normal, which translates into 177 patients a day, 35% of whom are patients with flu-like symptoms," she said.

Since September, CHEO has seen 20 confirmed cases of swine flu, but the majority of those patients were sent home soon after admission.

Fuller said the hospital is prepared for the worst.

"We have a pandemic plan in place to react to the needs of the region," she said.

"If we need to implement it, we will."

Responding to reports the EOHU is labeling Eastern Ontario a "hotspot" for H1N1, Ottawa's chief medical officer, Dr. Isra Levy, said there has been a notable increase in influenza in the province.

"You do see little pockets show up like Kingston . . . and Ottawa has also seen significantly increased activity over the past two to three weeks as well."

— With files from Michael Peelin