Thunder Bay District Health Unit officials have confirmed there is a community outbreak of the H1N1 flu virus in the city.
Associate medical officer of health Janet Demille said there have been 40 lab-confirmed cases of H1N1 or influenza A in the city in the last month and one confirmed death.
That's only the tip of the iceberg, she said.
"We believe that the number of cases is on the rise right now, that we anticipate it will peak in about week," she said Monday.
"Then it will decline but it will take probably another five weeks before it's back to normal levels."
The number of people with flu symptoms visiting the emergency room has also risen and Demille said there are always people who don't report their illness.
"There are many surveillance systems in place to monitor flu activity in the province and what's known right now is that Thunder Bay and parts of Northwestern Ontario have the highest rates of this type of influenza right now," she said.
Influenza can range from a mild illness of muscle aches, fever and fatigue to more serious symptoms like shortness of breath, cough and chest pains.
A healthy person can fight off the virus in 10 to 12 days, but for people with underlying health conditions or those who are elderly or young children, the virus is more severe.
Those vulnerable groups of people can end up in the hospital, sometimes on a ventilator.
"There's always concern with influenza because of the potential for severe illness and death associated with that," said Demille.
"We know every year there are people who die of influenza particularly among the vulnerable group. We're always concerned when it hits here, when it hits Thunder Bay."
People can avoid the flu by washing their hands regularly, coughing and sneezing into their sleeve instead of their hands and by getting the flu vaccination.
