What is whooping cough?

http://www.medicinenet.com/pertussis/article.htm
Whooping cough (pertussis) is an acute, highly contagious respiratory infection that is caused by a bacterium. The first outbreaks of pertussis were described in the 16th century. The bacterium responsible for the infection, Bordetella pertussis, was not isolated until 1906. Each year, 5,000-7,000 cases of whooping cough (pertussis) are recorded each year in the United States. The incidence of pertussis has been steadily increasing since the 1980’s.
Whooping cough (pertussis) commonly affects infants and young children but can be prevented with immunization with pertussis vaccine. Pertussis vaccine is most commonly given in combination with the vaccines for diphtheria and tetanus in the vaccine known as “DPT.” (Pertussis is the "P" in the DPT vaccine.) Immunity from the DPT vaccine wears off, so many teenagers and adults get whooping cough (pertussis).
Treatment of whooping cough is supportive, meaning that treatment is directed at the symptoms, e.g., cough; however, young infants often need hospitalization if the coughing becomes severe.
What are the stages and symptoms of whooping cough?
The first stage of whooping cough is known as the catarrhal stage. In the catarrhal stage, which typically lasts from one to two weeks, an infected person has symptoms characteristic of an upper respiratory infection, including;
runny nose
sneezing
low-grade fever
mild, occasional cough, similar to the common cold
The cough gradually becomes more severe, and after one to two weeks, the second stage begins. It is during the second stage (the paroxysmal stage) that the diagnosis of whooping cough usually is suspected. The second stage is characterized by:
Bursts (paroxysms) of coughing, or numerous rapid coughs, apparently due to difficulty expelling thick mucus from the airways in the lungs. Bursts of coughing increase in frequency during the first one to two weeks, remain constant for two to three weeks, and then gradually begin to decrease in frequency.
At the end of the bursts of rapid coughs, a long inspiratory effort (breathing in) is usually accompanied by a characteristic high-pitched “whoop”.
During an attack, the individual may become cyanotic (turn blue) from lack of oxygen..
Children and young infants appear especially ill and distressed.
Vomiting (referred to by doctors as posttussive vomiting) and exhaustion commonly follow the episodes of coughing.
The person usually appears normal between episodes.
Paroxysmal attacks occur more frequently at night, with an average of 15-24 attacks per 24 hours.
The paroxysmal stage usually lasts from one to six weeks but may persist for up to ten weeks.
Infants under six months of age may not have the strength to have a whoop, but they do have paroxysms of coughing.
The third stage of whooping cough is the recovery, or convalescent stage. In the convalescent stage, recovery is gradual. The cough becomes less paroxysmal and usually disappears over two to three weeks; however, paroxysms often recur with subsequent respiratory infections for many months.

Can adults get whooping cough?
Although whooping cough is considered to be an illness of childhood, adults may also develop the disease. The illness usually is milder in adults than in children, but the duration of the paroxysmal cough is just as long as in children. The characteristic “whoop” that occurs after paroxysmal bouts of coughing is recognized in only 20-40% of adults with whooping cough. Immunity from the pertussis vaccine decreases over time but does not necessarily disappear, Adults who do become infected may have retained a partial degree of immunity against the infection, and this can result in a milder illness. Whooping cough in adults is more common than usually appreciated, accounting for up to 7% of adult illnesses that cause coughing each year. Infected adults are a reservoir (source) of infection for children.
How is whooping cough diagnosed?
When a patient has the typical symptoms of whooping cough, the diagnosis can be made from the clinical history. However, the disease and its symptoms, including its severity, can vary among affected individuals. In cases where the diagnosis is not certain or a doctor wants to confirm the diagnosis, laboratory tests can be carried out. Culture of the bacterium Bordetella pertussis from nasal secretions can establish the diagnosis. Another test that has been used to successfully identify the bacterium and diagnose pertussis is the polymerase chain reaction (PCR) test that can identify genetic material from the bacterium in nasal secretions.
How is whooping cough treated?
Antibiotics directed against Bordetella pertussis can be effective in reducing the severity of pertussis when administered early in the course of the disease. Antibiotic therapy can also help reduce the risk of transmission of the bacterium to other household members as well as to others who may come into contact with an infected person. Unfortunately, most people with pertussis are diagnosed later with the condition in the second (paroxysmal) stage of the disease. Treatment with antibiotics is recommended for anyone who has had the disease for less than 21 days. It is unclear whether antibiotics have any benefit for persons who have been ill with pertussis for longer periods, although antibiotic therapy is still often considered for this group. There is no proven effective treatment for the paroxysms of coughing that accompany pertussis.

Complications of whooping cough (pertussis)
Young infants are at highest risk for whooping cough (pertussis) and for pertussis-associated complications. The most common complication and the cause of most pertussis-related deaths, is secondary bacterial pneumonia. (Secondary bacterial pneumonia is bacterial pneumonia that follows another infection of the lung, be it viral or bacterial. Secondary pneumonia is caused by a different virus or bacterium than the original infection.) Data from 1997-2000 indicate that secondary pneumonia occurred among 5.2% of all reported pertussis cases, and among 11.8% of infants less than six months of age. Pertussis can cause death in young children; 13 children died from the infection in 2003. Most of the pertussis-related deaths have occurred in children who have not been vaccinated or who are too young to have received the vaccine.
Other possible complications of pertussis include seizures, encephalopathy (abnormal function of the brain due to decreased oxygen delivery to the brain), reactive airway disease (asthma), and malnutrition.
Addendum: Whooping cough on the rise in California
The California Health Department announced in the fall of 2005 that the number of people developing whooping cough is increasing in California. For the first eight months of the year, the number of cases reported in California (1,276) was almost triple the number of cases reported during the same period in 2004 (450). The number of deaths and illnesses from whooping cough reported through August, 2005, had already surpassed the totals for the entire year of 2004. Other areas of the United States are experiencing the same trend.
For immunization information on pertussis for children, adolescents, and adults, please visit the following areas:
Immunizations (Vaccination) for Adolescents and Adults
Immunizations (Vaccinations) for Infants and Children