Whooping cough

Whooping cough, also known as pertussis, is a highly contagious disease whichcauses classic spasms (paroxysms) of uncontrollable coughing, followed by asharp, high-pitched intake of air which creates the characteristic "whoop" ofthe disease's name.

Whooping cough is caused by a bacteria called Bordatella pertussis. B. pertussis causes its most severe symptoms by attaching itself to those cells in the respiratory tract which have cilia. Cilia are small, hair-likeprojections 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 which 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 both the disease and for serious complications and death.Apparently, exposure to B. pertussis bacteria earlier in life gives aperson some immunity against infection with it later on. Subsequent infections resemble the common cold.

Whooping cough has four somewhat overlapping stages: incubation, catarrhal stage, paroxysmal stage, and convalescent stage.

An individual usually acquires B. pertussis by inhaling droplets infected with the bacteria coughed into the air by someone already suffering withthe infection. Incubation is the symptomless period of 7-14 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, poor appetite, and an extremely runnynose (rhinorrhea). This stage lasts about 10-14 days.

The paroxysmal stage, lasting two to four weeks, begins with the developmentof 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 mucous which narrow the breathing tubes, causing the patient to struggle to getair into his/her lungs; the effort results in intense exhaustion. The paroxysms (spasms) can be induced by overactivity, feeding, crying, or even overhearing someone else cough.

The mucus which is produced during the paroxysmal stage is thicker and more difficult to clear than the more watery mucus of the catarrhal stage, and thepatient becomes increasingly exhausted attempting to clear the respiratory tract through coughing. Severely ill children may have great difficult maintaining the normal level of oxygen in their systems, and may appear somewhat blueafter a paroxysm of coughing, due to the low oxygen content of their blood.Such children may also suffer from swelling and degeneration of the brain (encephalopathy), which is believed to be caused both by lack of oxygen to the brain during paroxysms, and also by bleeding into the brain caused by increased pressure during coughing. Seizures may result from decreased oxygen to thebrain. Some children have such greatly increased abdominal pressure during coughing that hernias result (hernias are the abnormal protrusion of a loop ofintestine through a weak area of muscle). Another complicating factor duringthis phase is the development of pneumonia from infection with another bacterial agent; the bacteria takes 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, especiallywhen 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 the flu, or asimple 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 pertussis (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 thenose). 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 will 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, todecrease 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.

Just under one percent 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:

  • Severe pneumonia, perhaps with accompanying encephalopathy
  • Extreme weight loss, weakness, and metabolic abnormalities due to persistent vomiting during paroxysms of coughing
  • Other pre-existingconditions, so that the patient is already in a relatively weak, vulnerablestate (such conditions may include low birth weight babies, poor nutrition, infection with the measles virus, presence of other respiratory or gastrointestinal infections or diseases).

The mainstay of prevention lies in programs similar to the mass immunizationprogram 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, has greatly reduced the incidence of whooping cough.

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