Whooping Cough Health Article

Definition

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

Description

Whooping cough is caused by a bacteria called Bordetella pertussis. B. pertussis causes its most severe symptoms by attaching itself to those 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, cleansing function, mucus and cellular debris accumulate and cause constant irritation to the respiratory tract, triggering coughing and increasing further mucus production.

Whooping cough exists throughout the world. While people of any age can contract the disease, 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 individuals some immunity against infection with it later on. Subsequent infections resemble the common cold.

Demographics

According to the Centers for Disease Control and Prevention, since 1990, the reported incidence of pertussis has increased in the United States. Peaks occur at three to four year intervals. Since 1990, 14 states reported the number of cases of whooping cough to be more than two per 100,000 in the population. A high proportion of those cases occurred in persons aged ten years or older.

Nearly 75 percent of pertussis cases reported worldwide are in children; half of those children affected require hospitalization. Prior to effective immunization programs in the United States, pertussis was the major cause of death from infectious disease among individuals under the age of 14. Because developing countries as of 2004 did not have widespread immunization available, there continue to be about 50 million cases of pertussis every year across the globe, with 300,000 leading to death. About 38 percent of all hospitalizations from pertussis are in babies under the age of six months.

Causes and symptoms

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 with the infection. Incubation is the asymptomatic period (time when no evidence of disease is present) of seven to 14 days after breathing in the B. pertussis bacteria, 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. People have teary eyes, sneezing, fatigue, poor appetite, and an extremely runny nose (rhinorrhea). This stage lasts approximately ten days to two weeks.

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 increased mucus, which narrow the breathing tubes, causing people to struggle to get air into their lungs; the effort results in intense exhaustion. The paroxysms (spasms) can be induced by over activity, feeding, crying, or even overhearing someone else cough.

The mucus that is produced during the paroxysmal stage is thicker and more difficult to clear than the more watery mucus of the catarrhal stage. Affected persons become increasingly exhausted when attempting to clear the respiratory tract through coughing. Severely ill children may have great difficulty maintaining the normal level of oxygen in their systems and may appear somewhat blue after 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 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. Another complicating factor during this phase is the development of pneumonia from infection with another agent. The second pathogen successfully invades due to the person's already-weakened condition.

If individuals survive 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 person contracts a cold, or other respiratory infection.