By MIKE STOBBE, AP Medical Writer
ATLANTA (AP) -- Health officials say the nation is on track to have the worst year for whooping cough in more than five decades.
Nearly 18,000 cases have been reported so far -- more than twice last year's total. At this pace, the number of whooping cough cases will surpass every year since 1959.
Whooping cough, or pertussis, is a highly contagious bacterial disease. It causes children to make a whooping sound as they gasp for breath.
In rare cases it can be fatal, and the Centers for Disease Control and Prevention says nine children have died so far this year.
The agency is urging adults and especially pregnant women to get vaccinated so they don't spread it to infants who are too young to get the vaccine.