21,000 cases of whooping cough reported last year

ATLANTA – More than 21,000 people got whooping cough last year, many of them children and teens. That’s the highest number since 2005 and among the worst years in more than half a century, U.S. health officials said Wednesday.

They are puzzled by the sharp rise in cases. The vaccine against whooping cough is highly effective in children, and vaccination rates for kids are good.

The disease is very contagious and in rare cases can be fatal, especially for babies too young to be vaccinated. Whooping cough starts like a cold but leads to severe coughing that can last for weeks.

California appeared to be the hardest-hit state last year, with state health officials reporting more than 8,300 cases.