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Pertussis

(Whooping Cough)

By Larry M. Bush, MD, Maria T. Perez, MD

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Patient Education

Pertussis is a highly communicable disease occurring mostly in children and adolescents and caused by Bordetella pertussis. Symptoms are initially those of nonspecific URI followed by paroxysmal or spasmodic coughing that usually ends in a prolonged, high-pitched, crowing inspiration (the whoop). Diagnosis is by nasopharyngeal culture, PCR, and serologic assays. Treatment is with macrolide antibiotics.

Pertussis is endemic throughout the world. Its incidence in the US cycles every 3 to 5 yr. Pertussis occurs only in humans;.there are no animal reservoirs.

Transmission is mainly via aerosols of B. pertussis (a small, nonmotile, gram-negative coccobacillus) from infected patients, particularly during the catarrhal and early paroxysmal stages. The infection is highly contagious and causes disease in ≥ 80% of close contacts. Transmission by contact with contaminated articles is rare. Patients are usually not infectious after the 3rd wk of the paroxysmal phase.

Pertussis is the only vaccine-preventable childhood disease that is increasing in incidence. In the US, the case rate in the 1980s was at an all-time low of about 1/100,000 population, which, by 2014, increased to about 10/100,000. The increase is due to immunity waning in previously vaccinated adolescents and adults and to parents refusing to vaccinate their children (see Anti-Vaccination Movement). Such unprotected patients may become ill; furthermore, unprotected adolescents and adults are an important reservoir for B. pertussis and are thus often the source of infection for unprotected infants < 1 yr (who have had the highest increase in annual incidence and the highest case fatality rate [ 1]).

In the US, there were 32,971 pertussis cases and 13 deaths in 2014 ( 2). Deaths occurred inf all age groups, but the incidence was highest in infants < 6 mo and most deaths (8 of 13) occurred in infants < 3 mo. Most deaths are caused by bronchopneumonia and cerebral complications. Pertussis is also serious in the elderly.

Pertussis Incidence by Age, 2014

Age

Number of Cases (%)

Incidence per 100,000

< 6 mo

3,330 (10.1)

169

6–11 mo

875 (2.7)

44.4

1–6 yr

6,082 (18.5)

25.1

7–10 yr

5,576 (16.9)

34

11–19 yr

11,159 (33.8)

29.6

≥ 20 yr

5,839 (17.7)

2.2

Unknown

110 (0.3)

N/A

Based on National Center for Immunization and Respiratory Diseases Division of Bacterial Diseases : 2014 Final Pertussis Surveillance Report. Centers for Disease Control and Prevention, 2015.

One attack does not confer lifelong natural immunity, but secondary attacks and infections in previously vaccinated adolescents and adults whose immunity has waned are usually mild and often unrecognized.

Diseases caused by pertussis

Respiratory complications, including asphyxia in infants, are most common. Otitis media occurs frequently. Bronchopneumonia (common among the elderly) may be fatal at any age.

Seizures are common among infants but rare in older children.

Hemorrhage into the brain, eyes, skin, and mucous membranes can result from severe paroxysms and consequent anoxia. Cerebral hemorrhage, cerebral edema, and toxic encephalitis may result in spastic paralysis, intellectual disability (mental retardation), or other neurologic disorders.

Umbilical herniation and rectal prolapse occasionally occur.

Parapertussis

This disease, caused by B. parapertussis, may be clinically indistinguishable from pertussis but is usually milder and less often fatal.

Reference

Symptoms and Signs

The incubation period averages 7 to 14 days (maximum 3 wk). B. pertussisinvades respiratory mucosa, increasing the secretion of mucus, which is initially thin and later viscid and tenacious. Uncomplicated disease lasts about 6 to 10 wk and consists of 3 stages:

  • Catarrhal

  • Paroxysmal

  • Convalescent

The catarrhal stage begins insidiously, generally with sneezing, lacrimation, or other signs of coryza; anorexia; listlessness; and a troublesome, hacking nocturnal cough that gradually becomes diurnal. Hoarseness may occur. Fever is rare.

After 10 to 14 days, the paroxysmal stage begins with an increase in the severity and frequency of the cough. Repeated bouts of 5 rapidly consecutive forceful coughs occur during a single expiration and are followed by the whoop—a hurried, deep inspiration. Copious viscid mucus may be expelled or bubble from the nares during or after the paroxysms. Vomiting is characteristic. In infants, choking spells (with or without cyanosis) may be more common than whoops.

Pertussis in a child, without whooping. Pertussis causes paroxysmal coughing; only about half of patients develop classic whooping. In this recording, the child coughs without inspiration until she has emptied her lungs of air, then breathes in. There is a slight pause between the paroxysm and inspiration. In severe cases of pertussis, this pause may be long enough to qualify as apnea; children may become cyanotic, and the apnea may be life threatening.

Whooping Cough (Paroxysm)

Audio file courtesy of Doug Jenkinson, MD.

Pertussis in a child, with whooping. Pertussis causes paroxysmal coughing; only about half of patients develop classic whooping. In this recording, the child coughs without inspiration until she has emptied her lungs of air, then breathes in with a whoop. The whoop is caused by vocal cord adduction during inspiration.

Whooping Cough (Classic Whoop)

Audio file courtesy of Doug Jenkinson, MD.

Pertussis in an adult, with whooping. In this recording, the patient coughs without inspiration until he has emptied his lungs of air, then breathes in with a whoop. The whoop is caused by vocal cord adduction during inspiration.

Whooping Cough (Adult Patient)

Audio file courtesy of Doug Jenkinson, MD.

Symptoms diminish as the convalescent stage begins, usually within 4 wk of onset. Average duration of illness is about 7 wk (range 3 wk to 3 mo or more). Paroxysmal coughing may recur for months, usually induced in the still sensitive respiratory tract by irritation from a URI.

Diagnosis

  • Nasopharyngeal cultures and PCR testing

The catarrhal stage is often difficult to distinguish from bronchitis or influenza. Adenovirus infections and TB should also be considered.

Cultures of nasopharyngeal specimens are positive for B. pertussis in 80 to 90% of cases in the catarrhal and early paroxysmal stages. Because special media and prolonged incubation are required, the laboratory should be notified that pertussis is suspected. Specific fluorescent antibody testing of nasopharyngeal smears accurately diagnoses pertussis but is not as sensitive as culture. PCR testing of nasopharyngeal samples is the most sensitive and preferred test. The WBC count is usually between 15,000 and 20,000/μL but may be normal or as high as 60,000/μL, usually with 60 to 80% small lymphocytes.

Parapertussis is differentiated by culture or the fluorescent antibody technique.

Treatment

  • Supportive care

  • Erythromycin or azithromycin

Hospitalization with respiratory isolation is recommended for seriously ill infants. Isolation is continued until antibiotics have been given for 5 days.

In infants, suction to remove excess mucus from the throat may be lifesaving. O2 and tracheostomy or nasotracheal intubation is occasionally needed. Expectorants, cough suppressants, and mild sedation are of little value. Because any disturbance can precipitate serious paroxysmal coughing with anoxia, seriously ill infants should be kept in a darkened, quiet room and disturbed as little as possible. Patients treated at home should be isolated, particularly from susceptible infants, for at least 4 wk from disease onset and until symptoms have subsided.

Antibiotics given during the catarrhal stage may ameliorate the disease. After paroxysms are established, antibiotics usually have no clinical effect but are recommended to limit spread. Preferred drugs are erythromycin 10 to 12.5 mg/kg po q 6 h (maximum 2 g/day) for 14 days or azithromycin 10 to 12 mg/kg po once/day for 5 days. Trimethoprim/sulfamethoxazole may be substituted in patients ≥ 2 mo who are intolerant of or hypersensitive to macrolide antibiotics. Antibiotics should also be used for bacterial complications (eg, bronchopneumonia, otitis media).

Prevention

Active immunization against pertussis is part of standard childhood vaccination. Five doses of acellular pertussis vaccine are given (usually combined with diphtheria and tetanus [DTaP]) at age 2, 4, and 6 mo; boosters are given at 15 to 18 mo and 4 to 6 yr.

Significant adverse effects from the pertussis component of the vaccine include

  • Encephalopathy within 7 days

  • Seizure, with or without fever, within 3 days

  • Persistent, severe, inconsolable screaming or crying for ≥ 3 h

  • Collapse or shock within 48 h

  • Fever ≥ 40.5° C within 48 h

  • Immediate severe or anaphylactic reaction

These reactions contraindicate further use of pertussis vaccine; combined diphtheria and tetanus vaccine (DT) is available without the pertussis component. The acellular vaccine is better tolerated than the previously used vaccine that contains numerous cell components and is the currently available preparation. Neither vaccination nor natural disease confers lifelong protective immunity against pertussis or reinfection. Immunity tends to wane 5 to 10 yr after the last vaccine dose is given.

A single booster with Tdap (containing lower doses of the diphtheria and pertussis components than the childhood DTaP) instead of Td is recommended for all adults after age 19 yr (including those > 65 yr) as well as before pregnancy; it should be given during each pregnancy after 20 wk gestation (preferably at 27 to 36 wk gestation). These newer recommendations are intended to decrease risk of spread of pertussis from susceptible adolescents and adults to unprotected infants.

Immunity after natural infection lasts about 20 yr. Passive immunization is unreliable and is not recommended.

Close contacts < 7 yr who have had < 4 doses of vaccine should be vaccinated. Contacts of all ages, whether vaccinated or not, should receive a 10-day course of erythromycin 500 mg po qid or 10 to 12.5 mg/kg po qid.

Key Points

  • Pertussis is a respiratory infection that can occur at any age but is most common and most likely to be fatal in young children, particularly infants < 6 mo.

  • A catarrhal stage with URI symptoms is followed by a paroxysmal stage with repeated bouts of rapid, consecutive coughs followed by a hurried, deep inspiration (the whoop).

  • The illness lasts about 7 wk, but cough may continue for months.

  • Diagnose using PCR testing or nasopharyngeal cultures; special media are required.

  • Treat with a macrolide antibiotic to ameliorate disease (during the catarrhal stage) or minimize transmission (during the paroxysmal stage and later).

  • Prevent the disease using acellular pertussis vaccine as part of scheduled immunizations (including a booster for adults), and treat close contacts with erythromycin.

  • Neither having the disease nor being vaccinated provides lifelong protection, although any subsequent disease tends to be milder.

Resources In This Article

* This is the Professional Version. *