Questions & Answers

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What causes pertussis?
Pertussis is caused by a bacterium, Bordetella pertussis.

How does pertussis spread?
Pertussis is spread through the air by infectious droplets and is highly contagious.

How long does it take to show signs of pertussis after being exposed?
The incubation period of pertussis is commonly seven 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 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.

How serious is pertussis?
Pertussis can be a very serious disease, especially for infants. Rates of hospitalization and complications increase with decreasing age. Of the 100 deaths from pertussis during 2000-2004, 76 occurred in infants age one month or younger. Infants younger than age one year accounted for 19% of pertussis cases and 92% of pertussis deaths in the United States during 2000-2004. As noted above in the section on symptoms, the breathing difficulties associated with this disease can be very distressing and scary for the patient and his or her family.

Although adults are less likely than infants to become seriously ill with pertussis, most make repeated visits for medical care and miss work, especially when pertussis is not initially considered as a reason for their long-term cough. In addition, adults with pertussis infection have been shown to be an important source of infection to infants with whom they have close contact.

What are possible complications from pertussis?
Again, 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. In 1997-2000, 0.8% of all cases, and 1.4% of cases under six months of age, involved seizures.

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 do I know if my child has pertussis?
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 (through the nose).

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 DTaP vaccine series if they have not already done so. If they have completed their primary four dose series, but have not had a dose within the last three years, they should be given a booster dose.

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).

How common is pertussis in the United States?
Before a vaccine against pertussis was available, whooping cough was a major cause of childhood sickness and death in the United States. From 1940-1945, over one million cases of pertussis were reported.

With the introduction of a vaccine in the late 1940s, the number of pertussis cases reported nationally fell from approximately 200,000 a year in the pre-vaccine era to a low of 1,010 cases in 1976.

Unfortunately, since then, a steady increase in reported pertussis cases has occurred, with proportionately more cases in adults and adolescents. In 2004, 25,827 cases of pertussis were reported to CDC, the highest number since 1959. Adults (age 19-64 years) accounted for 27% of these cases. The increase in reported cases of pertussis might be due to a real increase in the disease rate or to increasing availability and use of testing technology to confirm cases and increasing healthcare provider awareness and reporting of pertussis.

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 per the routine schedule.

Questions and answers about pertussis vaccine

Technically reviewed by the Centers for Disease Control and Prevention, February 2007