Whooping cough, also known as pertussis, is a highly contagious disease that causes spasms (paroxysms) of uncontrollable coughing, followed by a sharp, high-pitched intake of air that creates the characteristic “whoop” of the disease's name.
Pertussis occurs equally in males and females. Whites make up the large majority at over 85% of cases diagnosed. People under the age of 20 years make up over 75% of cases, most of these being reported in children under the age of one or between the ages of 10 and 19. Because the whooping cough vaccination does not provide lifelong immunity and immunity is no longer evident after 12 years, people must be revaccinated in order to be protected.
Whooping cough is caused by a bacterium called Bordatella pertussis. B. pertussis causes its most severe symptoms by attaching itself to cells in the respiratory tract that have cilia. Cilia are small, hair-like projections that beat continuously, and serve to constantly sweep the respiratory tract clean of such debris as mucus, bacteria, viruses, and dead cells. When B. pertussis interferes with this normal janitorial function, mucus and cellular debris accumulate and cause constant irritation to the respiratory tract, triggering coughing and increasing further mucus production.
Whooping cough is a disease that exists throughout the world. While people of any age can contract whooping cough, children under the age of two are at the highest risk for the disease and for serious complications and death. Apparently, exposure to B. pertussis bacteria earlier in life gives a person some immunity against infection with it later on. Subsequent infections resemble the common cold.
Whooping cough has four somewhat overlapping stages: incubation, the catarrhal stage, the paroxysmal stage, and the convalescent stage.
An individual usually acquires B. pertussis by inhaling droplets infected with the bacteria coughed into the air by someone with the infection. Incubation is the symptomless period of 7 to 14 days after breathing in the B. pertussis bacteria, and during which the bacteria multiply and penetrate the lining tissues of the entire respiratory tract.
The catarrhal stage is often mistaken for an exceedingly heavy cold. The patient has teary eyes, sneezing, fatigue, a poor appetite, and an extremely runny nose (rhinorrhea). This stage lasts about 10 to 14 days.
The paroxysmal stage, lasting two to four weeks, begins with the development of the characteristic whooping cough. Spasms of uncontrollable coughing, the “whooping” sound of the sharp inspiration of air, and vomiting are all hallmarks of this stage. The whoop is believed to occur due to inflammation and mucus, which narrow the breathing tubes, causing the patient to struggle to get air into his or her lungs; the effort results in intense exhaustion. The paroxysms (spasms) can be induced by activity, feeding, crying, or even overhearing someone else cough.
The mucus produced during the paroxysmal stage is thicker and more difficult to clear than the more watery mucus of the catarrhal stage, and the patient becomes increasingly exhausted attempting to clear the respiratory tract through coughing. Severely ill children may have great difficulty maintaining the normal level of oxygen in their system and may appear somewhat blue (cyanotic) after a paroxysm of coughing, due to the low oxygen content of their blood. Such children may experience swelling and degeneration of the brain (encephalopathy), which is believed to be caused both by lack of oxygen to the brain during paroxysms and by bleeding into the brain caused by increased pressure during coughing. Seizures may result from decreased oxygen to the brain. Some children have such greatly increased abdominal pressure during coughing that hernias result. (Hernias are the abnormal protrusion of a loop of intestine through a weak area of muscle.) Another complicating factor during this phase is the development of pneumonia from infection with another bacterial agent; the bacteria take hold due to the patient's already-weakened condition.
If the patient survives the paroxysmal stage, recovery occurs gradually during the convalescent stage, usually taking about three to four weeks. However, spasms of coughing may continue to occur over a period of months, especially when a patient contracts a cold or other respiratory infection.
Diagnosis based just on the patient's symptoms is not particularly accurate, as the catarrhal stage may appear to be a heavy cold, a case of influenza, or a simple bronchitis. Other viruses and tuberculosis infections can cause symptoms similar to those found during the paroxysmal stage. The presence of a pertussis-like cough along with an increase of certain specific white blood cells (lymphocytes) is suggestive of whooping cough. However, cough can occur from other pertussis-like viruses.
The most accurate method of diagnosis is to culture (grow on a laboratory plate) the organisms obtained from swabbing mucus out of the nasopharynx (the breathing tube continuous with the nose). B. pertussis can then be identified by examining the culture under a microscope.
Treatment with the antibiotic erythromycin is helpful only at very early stages of whooping cough, during incubation and early in the catarrhal stage. After the cilia and the cells bearing those cilia are damaged, the process cannot be reversed. Such a patient will experience the full progression of whooping cough symptoms; symptoms only improve when the old, damaged lining cells of the respiratory tract are replaced over time with new, healthy, cilia-bearing cells. However, treatment with erythromycin is still recommended to decrease the likelihood of B. pertussis spreading. In fact, all members of the household where a patient with whooping cough lives should be treated with erythromycin to prevent the spread of B. pertussis throughout the community.
The only other treatment is supportive and involves careful monitoring of fluids to prevent dehydration; rest in a quiet, dark room to decrease paroxysms; and suctioning of mucus. Patients should be hospitalized if at risk for complication, such as infants from birth to six months of age.
Just under 1% of all cases of whooping cough cause death. Children who die of whooping cough usually have one or more of the following three conditions present:
The mainstay of prevention lies in programs similar to the mass immunization program in the United States, which begins immunization inoculations when infants are two months old. The pertussis vaccine, most often given as one immunization together with diphtheria and tetanus (DTP or DTaP), has greatly reduced the incidence of whooping cough.
See also Bronchitis ; Diphtheria ; Tuberculosis ; Vaccination ; Viruses .
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American Academy of Family Physicians, P.O. Box 11210, Shawnee Mission, KS, 66207, (913) 906–6000, (800) 274-2237, Fax: (913) 906–6075, http://familydoctor.org/familydoctor/en/about/contact-us.html , http://familydoctor.org .
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National Institute of Allergy and Infectious Diseases Office of Communications and Government Relations, 6610 Rockledge Dr., MSC 6612, Bethesda, MD, 208926612, (301) 496–5717, (866) 284–4107, or TDD: (800) 877–8339 (for hearing impaired), Fax: (301) 402-3573, firstname.lastname@example.org, http://www3.niaid.nih.gov .
World Health Organization, Avenue Appia 20, 1211 Geneva 27, Switzerland, +22 41 791 21 11, Fax: +22 41 791 31 11, email@example.com, http://www.who.int .
Rosalyn Carson-DeWitt, MD
Revised by Tish Davidson, AM