Whooping cough is evolving in response to its vaccine. Want proof? In a new study, researchers found 30 percent of whooping cough bacteria in Australia have evolved.

This is not your parents’ pertussis. Over the last few years, this once-common childhood illness, also known as whooping cough, has evolved in response to its own vaccine, according to a new study from the U.S. Centers for Disease Control and Prevention.

There were more cases of whooping cough in the US in 2012 than in any year since 1955, provisional data suggest. The disease, which still sounds a little old-fashioned to these young ears, has been on the rise in America since 1980. What's going on?