What causes pertussis?

Pertussis, or whooping cough, is a disease of the respiratory tract caused by bacteria that live in the mouth, nose, and throat. Many children who contract pertussis have coughing spells that last four to eight weeks. The disease is most dangerous in infants. In 2000, an estimated 39 million cases and 297 000 deaths occurred worldwide, due to pertussis.

How does pertussis spread?

Pertussis is spread through the air by infectious droplets produced by coughing or sneezing and is highly contagious.

How long does it take to show signs of pertussis after being exposed?

The incubation period of pertussis is commonly 7 to 10 days, with a range of 5-21 days.

What are the symptoms of pertussis?

Pertussis disease can be divided into three stages:

  • Catarrhal stage: can last 1-2 weeks and includes a runny nose, sneezing, low-grade fever, and a mild cough (all similar symptoms to the common cold).
  • Paroxysmal stage: usually lasts 4-6 weeks, but can persist for up to 10 weeks. The characteristic symptom is a burst, or paroxysm, of numerous, rapid coughs. At the end of the paroxysm the patient suffers from a long inhaling effort that is characterized by a high-pitched whoop (hence the name, “whooping cough”). Infants and young children often appear very ill and distressed, and may turn blue (as they don’t get enough oxygen) and vomit.
  • Convalescent stage: usually lasts 2-6 weeks, but may last for months. Although the cough usually disappears after 2-3 weeks, paroxysms may recur whenever the patient suffers any subsequent respiratory infection. The disease is usually milder in adolescents and adults, consisting of a persistent cough similar to that found in other upper respiratory infections. However, these individuals are still able to transmit the disease to others, including unimmunized or incompletely immunized infants.
What are possible complications from pertussis?

Younger patients have a greater chance of complications from pertussis than older patients. The most common complication is secondary bacterial infection, which is the cause of most pertussis related deaths. Pneumonia occurs in one out of 20 cases. Infants are also more likely to suffer from such neurologic complications as seizures and encephalopathy, probably due to the reduction of oxygen supply to the brain. Other less serious complications include ear infection, loss of appetite, and dehydration. Adults with pertussis can have complications such as pneumonia (up to 5% of cases) and rib fracture from coughing (up to 4% of cases). Other reported side effects include (among others), loss of consciousness, female urinary incontinence, hernias, angina, and weight loss.

How pertussis is diagnosed?

The diagnosis of pertussis is usually made based on its characteristic history and physical examination. A laboratory test may be done, which involves taking a specimen from the back of the patient’s throat.

Is there a treatment for pertussis?

Antibiotics are somewhat helpful in treating pertussis. The drug of choice is usually erythromycin. This antibiotic should also be given for 14 days to all household and other close contacts of the patient to minimize transmission, regardless of age and vaccination status. All close contacts younger than seven years of age should complete their DTP vaccine series if they have not already done so. Patients also need supportive therapy such as bed rest, fluids, and control of fever.

How long is a person with pertussis contagious?

Persons with pertussis are most infectious during the catarrhal period and during the first two weeks after onset of the cough (approximately 21 days).

Can you get pertussis more than once?

Reinfection appears to be uncommon but does occur. With natural infection, immunity to pertussis will likely wane as soon as seven years following disease; reinfection may present as a persistent cough, rather than typical pertussis. Unfortunately, it is difficult to verify pertussis infection with existing laboratory methods. If someone has a recent culture-documented case of pertussis, he or she may not need immediate immunization against pertussis; however, a vaccine containing pertussis antigen will not be harmful, and they should continue on the routine immunization schedule for future protection against tetanus, diphtheria, and pertussis. If culture is lacking, even with a history of pertussis, do NOT withhold a dose of pertussis vaccine, if it is recommended as per the routine schedule.

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