Pertussis, also known as Whooping Cough, is filling the state's pediatric wards once again.
So far this year, there are 348 confirmed cases in Colorado.
There state's health department says there were about 12-hundred cases last year compared to 368 in 2003.
In El Paso County, there are now nine cases -- compared to none last year.
So who's getting hit the hardest? Health officials say 10-to 14-year olds because vaccinations start fading near adolescence.
Pertussis causes coughing spasms, and can lead to permanent disability or even death.
There is a vaccine for it. However, it's only for children six and under.