It killed 13 children, mostly infants, in 2003.
Before immunizations became widespread, an average of 147,000 people in the United States developed whooping cough every year and 9,000 died.
Whooping cough is common in countries where children do not receive vaccinations -- 294,000 people worldwide died of the illness in 2002, according to the World Health Organization.
It is making a resurgence in other developed countries, such as Britain. Germany began vaccinating teenagers against pertussis in 2000.
An upswing of reported cases in the past decade is a source of debate among health professionals, who attribute it to waning immunity in teenagers and adults and improved means of detecting the infection. Neither the vaccine nor the infection with the bacteria offers lifelong protection.
Beginning at two months of age, babies should be vaccinated against whooping cough, also known as pertussis, as part of an early childhood immunization series that includes diphtheria and tetanus.
Until last year, with the approval of a new type of vaccine for people ages 11 to 64, adolescents only got a booster shot for diphtheria and tetanus because the vaccine used in recent years was not approved for people over the age of 7 due to concern about possible side effects.
TRACKING AN OUTBREAK
New Trier High School had 26 confirmed cases of pertussis by November 16, or one third of all those reported in suburban Cook County. The school's first case was detected in late August when students returned from summer break. There have also been reports of sporadic cases at other high schools in the area.
Since early November, New Trier has been operating under directives from local health authorities to treat the situation as an outbreak.
"If your child has a cough, please do not send him or her to school," the local health department said in a letter to New Trier parents.
The high school has been trying to limit potential spread to other schools by canceling some athletic and extra-curricular events, circulating fact sheets, letters and e-mails, and keeping a close watch on students, faculty and staff for signs of the disease.
"We don't want to alarm everyone, so it's a big balancing act," said Dr. Catherine Counard, assistant medical director for communicable disease control at the Cook County Department of Public Health. "Whooping cough is a serious disease and we need to get this under control."
Whooping cough is tricky to diagnose because early symptoms are similar to other respiratory illnesses such as the common cold and bronchitis.
One telltale sign is a persistent dry cough. If detected early, the disease responds to antibiotics, but it is often diagnosed late and must be left to run its course.
Rarely life-threatening in teens or adults, small children are at risk for broken ribs, pneumonia and sometimes death. They typically get the disease from adults, making containment of an outbreak on the scale of New Trier's critical.
PRECAUTIONARY MEASURES
CDC recommends that adolescents and adults get the new tetanus-diphtheria-pertussis booster instead of the older vaccine that includes only tetanus and diphtheria. At New Trier, most of the cases were among older students who had not received the new shot.
"We now know that immunity to whooping cough wears off as we age," said Dr. Susan Rehm, medical director at the National Foundation for Infectious Diseases. "The nice news is that this is preventable through vaccination."
As New Trier battles its outbreak, there have been reports of cases of whooping cough at Children's Hospital in Boston and a high school in Palo Alto, California.
Trying to get a handle on the health status of more than 4,000 students spread over two school campuses has been no small feat, New Trier's Kahler recalled. Anyone with a sustained cough -- teachers and staff included -- has been sent home pending clearance from a doctor.
Kahler had to initially double her staff to six nurses and add a secretary just to keep up with extra paperwork, lab results, student whereabouts, community outreach and the endless stream of phone calls.
Preventive measures at the school have ranged from subtle to humorous. A large container of Purell hand sanitizer and Kleenex is now a staple in every classroom. Students were shown a film entitled "How to Do It In Your Sleeve," which offers a primer on minimizing the spread of germs when coughing.
But despite the school's best efforts, the outbreak has not been easy on the local community. Many pediatricians were not ready for the onslaught of requests for pertussis vaccine and parents have had difficulty seeking alternative sources.
"The numbers are much less now because the kids are getting cleared and getting treatment," said school superintendent Linda Yonke. "I hope we're through the worst."
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