MIAMI -

South Florida health officials say there has been a rise in the number of children infected with whooping cough.

The Miami Herald reports 26 cases have been confirmed in both Miami-Dade and Broward counties between Jan. 1 and July 9. Miami-Dade officials report another 10 probable cases.

Medical officials say the increase is likely caused by parents who have not had their children vaccinated.

Students in public schools are required to be vaccinated for whooping cough. There are exceptions, including for religious reasons.

Whooping cough, also known as pertussis, can merely be a bad cough in some people. It can linger for about three months. It can lead to pneumonia, seizures, shock and death.

Officials say children under 1 are most vulnerable