One factor is spotty vaccination.
Now researchers in Australia think they've filled in another piece of the puzzle there.
They say the vaccine is better at targeting some strains of the bacterium responsible for whooping cough, Bordetella pertussis, and that's allowing other strains to flourish.
Now this this doesn't mean the vaccine is no longer effective, says microbiologist Ruiting Lan of the University of New South Wales, who oversaw the research. "It is still quite important to stop the transmission" by getting vaccinated, he tells Shots.
