(AP File/Rich Pedroncelli)

Nurse Susan Peel gives a whooping cough vaccination to a student at Inderkum High School in Sacramento, California.

Illinois officials are seeing a rise in whooping cough cases in some collar counties. DuPage County has the most reported with almost 200 cases.

Health officials warned that it can be most dangerous for the young, elderly and people with weakened immune systems.

Dave Hass, public information officer for the DuPage County Health Department, said people should stay at home if they are sick.

“It is a disease that often goes on for many days and even weeks and is characterized by that whooping cough and it is something that can lead to more serious ramifications so people should seek medical care,” Hass said.

He added people can take precautions by getting immunized and washing their hands regulary.

The Illinois Department of Public Health has reported 1,019 whooping cough cases so far this year and 1,057 cases in 2010.

Meanwhile, school districts and health officials are seeing an increased number of whooping cough cases in southeast Wisconsin.

Milwaukee Health Department director Paul Biedrzycki says the city is seeing more cases in the past one to two weeks with 12 confirmed cases in November. he says that’s double the number of cases usually reported in November.

In Ozaukee County, public nursing supervisor Diana Noak says her department is getting widespread reports of pertussis in schools. the Mequon-Thiensville district reported at least four cases, none in public schools.

In Racine, Wisconsin,  Racine United School District is reporting what’s believed to be the district’s first case of whooping cough.

A letter was sent home Tuesday with students at Horlick High School. In it, district officials say they received confirmation of a case of pertussis at the school.

District spokeswoman Stacy Tapp says the student returned to classes Monday after completing the required five-day course of antibiotics. she says the student went to the doctor during the Thanksgiving break last week and began treatment.

Tapp declined to comment on the student’s age, grade level and gender.

Whooping cough is a contagious bacterial infection that affects the respiratory system.