Whooping cough: How to prevent kids from contracting disease With nearly 18,000 cases so far this year, health officials say this is shaping up to be the worst national epidemic in more than 50 years for the highly contagious disease. Worrisome numbers have been reported in more than a dozen states. What's a parent to do? Some advice: FIRST STEP: Make sure your child is up-to-date on vaccination…