Pertussis

Alternative names
Whooping cough

Definition
Pertussis is a highly contagious bacterial disease that affects the respiratory system. It produces spasms of coughing that may end in a high-pitched, deep inspiration (the “whoop”).

Causes, incidence, and risk factors

Pertussis, also known as whooping cough, is caused by infection with the Bordetella pertussis bacteria. The infection is spread through the air by droplets from the breath of an infected person. The incubation period is usually 7 days.

Whooping cough can affect people of any age. Prior to widespread immunization, the disease was most common in infants and young children. Now that most children are immunized before school age, a higher percentage of cases are seen among adolescents and adults.

However, about 40% of cases still occur in infants younger than 6 months of age. Early immunization can usually prevent this serious disease, which can sometimes be fatal or lead to permanent disability when it affects babies.

The bacteria invade the nose and throat, the breathing tube (trachea), and the lungs. The infection usually lasts 6 weeks. It starts with symptoms similar to the common cold, and progresses to spasms of coughing after 10 to 12 days.

The cough is characterized by 2 or 3 repeated coughs without inhaling. Typically, the person’s face becomes redder with each cough, then subtly bluish.

In children, the coughing spasm often ends with a characteristic “whoop” when breathing in. The whoop is rare in patients under 6 months of age and adults. It is most often seen in children between 6 months and 7 years old. Very young children, older kids, and adults usually just have severe cough spasms (several in a row) that may cause vomiting.

The child may momentarily lose consciousness at the end of a coughing spell. During this stage, there is heavy mucus production. Coughing spells may lead to vomiting. Pertussis should always be considered when vomiting occurs with coughing. In infants, choking spells are common.

Recovery begins about four weeks after symptoms begin and may take several weeks. Coughing spasms may return over the next several months, usually due to irritation from an upper respiratory infection.

Immunization may reduce the symptoms of pertussis in those cases where it does not produce complete immunity. However, when the symptoms are not obvious, pertussis may be difficult to diagnose.

Symptoms

     
  • runny nose  
  • severe cough - may be dry or may produce sputum  
  • slight fever (102°F or lower)  
  • severe coughing attacks may:       o involve difficulty breathing       o result in vomiting       o end in a high-pitched, crowing sound when inhaling, or end in a high-pitched “whoop”       o end in a momentary loss of consciousness  
  • diarrhea  
  • choking spells in infants  
  • choking when emotional

Signs and tests

The initial diagnosis is usually based on the symptoms. To know for sure, the health care provider may take a swab of nasal secretions, grow a culture for a week or more, and then test for pertussis. This can be an accurate way of confirming a pertussis diagnosis, but the results are obtained after treatment has probably begun. Thus, the culture has limited usefulness.

The swabbed nasal secretions can be tested more quickly several other ways. One test, called PCR, is quick and reliable but is a newer test that may be less widely available. An older test, called the DFA (direct fluorescent assay), gives quick results but is not as reliable.

Some patients may have a complete blood count that shows large numbers of lymphocytes (lymphocytosis).

Under 6 months of age, and particulary under 4 months, the main condition that mimics pertussis is pneumonia due to chlamydia trachomatis infection.

Treatment

Antibiotics may shorten the duration of the symptoms if started early enough. Unfortunately, most patients are only diagnosed after the period of time when antibiotics are most effective, and so generally antibiotics are not used. When they are used, antibiotics include erythromycin and similar drugs, tetracyclines for teens and adults, and amoxicillin for newborns.

Infants under 18 months of age require constant supervision because breathing may temporarily stop during coughing spells. Infants with severe cases should be hospitalized.

An oxygen tent with high humidity may be used. Intravenous fluid may be necessary if coughing spells are severe enough to prevent the patient from drinking enough fluids. Sedatives may be prescribed for young children.

Cough mixtures, expectorants, and suppressants are usually not helpful and should NOT be used.

Expectations (prognosis)
In older children, the prognosis is generally very good. Infants are the group at the highest risk. Infants less than 6 months of age have a 0.5% to 1% risk of death, which is why they need careful monitoring.

Complications

     
  • Pneumonia  
  • Convulsions  
  • Seizure disorder (permanent)  
  • Nose bleeds  
  • Ear infections  
  • Brain damage from lack of oxygen  
  • Bleeding in the brain (cerebral hemorrhage)  
  • Developmental retardation  
  • Slowed or stopped breathing (apnea)  
  • Death

Calling your health care provider

Call your health care provider if you or your child develops symptoms of pertussis.

Call 911 or get to an emergency room if the person has any of the following symptoms:

     
  • Bluish skin color, which indicates a lack of oxygen  
  • Periods of stopped breathing (apnea)  
  • Seizures or convulsions  
  • High fever  
  • Persistent vomiting  
  • Dehydration

Prevention

A DTaP vaccine (diphtheria, tetanus, pertussis) or pertussis-only vaccine helps protect children against this disease. Vaccination starts in infancy.

During epidemics, unimmunized children under age 7 should be excused from school and public gatherings and isolated from anyone known or suspected to be infected. This should last until 14 days after the last reported case.

Pertussis immunization is not 100% effective. Furthermore, the effect of childhood immunization begins to wear off after about 5 years, which is why previously immunized teens and adults can get pertussis. In these cases, the symptoms are usually milder and less “classic”.

During epidemics, health care workers, teens in school, or others with a high risk of exposure should consider a booster dose of the vaccine.

Johns Hopkins patient information

Last revised: December 6, 2012
by Dave R. Roger, M.D.

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