LETHBRIDGE, Alta. -- The death of a baby girl from whooping cough has Alberta health officials reminding people they should be immunized against the disease.

They say one-month-old Harper Whitehead died at Alberta Children's Hospital in Calgary last month from complications caused by pertussis.

Children under six months of age have little, if any, immunity to the cough, but cannot be vaccinated against it until they are older.

In March, Alberta Health Services declared an outbreak in southern Alberta where there have been 42 reported cases so far this year.

Dr. David Strong, acting medical health officer for the region, says it's important that anyone around babies be immunized.

Harper's aunt, Dani Whitehead, says her niece didn't have to die and is urging people to make sure their immunizations are up to date.

Pertussis is a highly contagious bacterial disease. It leads to severe coughing that causes children to make a distinctive whooping sound as they gasp for breath. In rare cases it can be fatal.