Officials at the Centers for Disease Control and Prevention in Atlanta said Wisconsin's incidence of the disease was 50.7 per 100,000 people through July 5 -- nearly 10 times the national average. Washington state had the second-highest rate, with 39.2 cases per 100,000 residents, the Wisconsin Center for Investigative Journalism reported in the Superior (Wis.) Telegram.
Through July 31, Wisconsin reported 3,496 cases of pertussis, or whooping cough, including 2,498 confirmed and 998 probable cases. Washington state reported 3,484 cases through Aug. 11.
Washington has declared an epidemic. Wisconsin has not, but Wisconsin health officials said they were taking appropriate steps, including encouraging vaccinations and booster shots and making sure infants are protected from unvaccinated people.
Infants are too young to get immunized from whopping cough so physicians advise parents and any other family members in contact with a baby to get vaccinated to protect the baby.
An unusual summer spike in whooping cough in Colorado -- mainly Denver and Boulder -- has prompted health officials to declare an epidemic and call for both children and adults to get immunized.
To date, 715 cases of whooping cough were tracked in Colorado compared to an average of 158 cases during the same period in each of the previous five years, health officials said.
"We are alerting the public to an epidemic number of pertussis cases in Colorado and are urging Coloradans to get vaccinated against pertussis," Dr. Chris Urbina, chief medical officer and executive director of the Colorado Department of Public Health and Environment, told the Denver Business Journal.