A spike in flu cases in Calgary has Alberta Health Services urging people to get immunized.

Of the 158 confirmed cases this season, 68 patients were so sick they needed to be hospitalized.

The number of flu cases spiked around this time last year too but they weren't as severe, said AHS medical officer Judy MacDonald.

“What we are seeing that is different this year is severity of illness in some of the hospitalized cases,” she said.

“Last year I don’t recall that we had that severe illness but we do have individuals that are in the intensive care unit now as we speak.”

AHS is reminding Calgarians to get a free flu shot before its four mass clinics close for the holidays on Saturday at 6:30 p.m. MT.

The clinics are at Brentwood Village Mall, the South Calgary Health Centre, Northgate Village and the Richmond Road Diagnostic Treatment Centre.

Shots are also available at family doctors’ offices and pharmacies.