Whooping cough infection continues in Chicago suburb
There has been an outbreak of whooping cough, or pertussis, at New Trier High School in Winnetka, Illinois, a suburb of Chicago. As of last Wednesday, twenty-nine students and one staff member had been diagnosed with this respiratory infection; this represents about 6% of all pertussis this year in the state of Illinois. Although infants are vaccinated against pertussis, the immunity wanes over time. Recently, a booster vaccine has become available for adolescents and adults; 95% of freshmen received the vaccine during their high school physicals this year and the only two freshman cases were in students who had not received the vaccine. Several extracurricular events have been cancelled to avoid spreading the disease to other schools, and the Cook County Public Health Department is working with New Trier to provide free vaccination to all students and staff. Those who decline immunization will probably be restricted from such events, and the Health Department has the authority to bar those students from attending school in order to prevent further spread of the disease.
Pertussis is a highly contagious infection of the respiratory tract; it is caused by the bacterium Bordetella pertussis. Attack rates are 80 to 100% among unimmunized household contacts, according to Harrison’s. About a week after infection, patients develop symptoms of the common cold; however, after one or two weeks, the cough becomes more prominent, occurring suddenly and in bursts. The fits may be followed by a sharp inwards breath, called a whoop. After two to four weeks, the coughing becomes less severe, but can continue for a few months. Up to a year later, viral infections may trigger the fits of coughing.
In infants, the disease is especially severe, and can lead to death. The development of a vaccine against pertussis has dramatically reduced the rates of infection and death. It was combined with immunizations against diphtheria and tetanus; the combination vaccine is termed “DTP.” The occurrence of some side effects led researchers to formulate a new vaccine that uses only components of Bordetella pertussis instead of whole cells, this “acellular” version is called “DTaP” and is now the version used in the United States; DTP is still used in many countries, especially developing ones. DTaP is given as a series at ages 2, 4, and 6 months, with repeat injections at 15–18 months and 4–6 years. However, this immunity fades over time, and adolescents and adults may be infected, though the disease is usually not as severe. However, it can still cause lengthy sickness and such people can easily transmit the disease to others. Infants less than a year old, still developing immunity, are at the highest risk.
Pertussis is usually milder in adolescents and adults. However, its effects can persist for months and complications may occasionally result—and of course, while infected, they can pass the disease on to others, including infants. Recently (around a year and a half ago), vaccines have been tested and licensed that can be used in those ages 10–64. It is administered as part of a combination called “TDaP.” Many countries, including the United States, recommend their routine use. Studies over the next years and decades will measure the magnitude of the effect; we may hope that the rates of pertussis will decline (after reaching a low point in 1976, cases of pertussis in the United States have started to rise, now about seven or eight times the 1976 level).