FISHERS, Ind. -- Two cases of whooping cough have been confirmed at a Hamilton County elementary school.

Hamilton Southeastern Schools notified parents on Friday that two students at Geist Elementary School had contracted the illness, also known as pertussis.

Parents were told not to send children to school if whooping cough, which is highly contagious, is suspected or diagnosed.

Indiana requires children be vaccinated against whooping cough at age 2, 4, 6 and 15 months, with a booster shot before entering kindergarten.

New immunization requirements state that children who are entering sixth grade through 12th grade must get another pertussis booster.

There were 400 reported cases of whooping cough in Indiana in 2009. Health experts said earlier this summer that they expected to see an uptick in the illness.

They said whooping cough is often tough to diagnose because it starts with symptoms similar to a cold. If caught early, pertussis is treatable with antibiotics.