Merck Manual

Please confirm that you are a health care professional

Loading

Pertussis

(Whooping Cough)

By

Larry M. Bush

, MD, FACP, Charles E. Schmidt College of Medicine, Florida Atlantic University;


Maria T. Vazquez-Pertejo

, MD, FCAP, Wellington Regional Medical Center

Last full review/revision Feb 2020| Content last modified Feb 2020
Click here for Patient Education
Topic Resources

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

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

Transmission is mainly via droplets of respiratory secretions that contain 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 week of the paroxysmal phase.

Pertussis is a 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 2018 provisional surveillance report by the Centers for Disease Control and Prevention (CDC) reported an incidence of 4.13/100,000 (1). The increase since the 1980s is due to

  • Immunity waning in previously vaccinated adolescents and adults

  • 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 year (who have had the highest increase in annual incidence and the highest case fatality rate [2]). Also, virulence of outbreak strains may be increasing.

In the US in 2018, there were 15,609 pertussis cases and 5 deaths (see table Pertussis Incidence by Age, 2018). The incidence per 100,000 was highest in infants < 6 months (72.8), and 3 of the 5 deaths occurred in infants < 1 year (1). Pertussis is also serious in older people.

Table
icon

Pertussis Incidence by Age, 2018

Age

Number of Cases (%)

Incidence per 100,000

< 6 months

1401 (9.0)

72.8

6–11 months

630 (4.0)

32.7

1–6 years

3232 (20.7)

13.5

7–10 years

1897 (12.2)

11.6

11–19 years

4922 (31.5)

13.0

≥ 20 years

3520 (22.6)

1.4

Unknown

7 (0.0)

N/A

Based on National Center for Immunization and Respiratory Diseases Division of Bacterial Diseases: 2018 Final Pertussis Surveillance Report. Centers for Disease Control and Prevention, 2019.

N/A = not applicable.

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 older people) may be fatal at any age.

Seizures are common among infants but are 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, or other neurologic disorders.

Umbilical hernia 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.

General references

Symptoms and Signs

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

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

Diagnosis

  • Nasopharyngeal cultures, direct fluorescent antibody testing, and polymerase chain reaction (PCR) testing

  • Serologic testing

The catarrhal stage is often difficult to distinguish from bronchitis or influenza. Adenovirus infections and tuberculosis 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. Paired acute and convalescent serologic testing may be helpful.

PCR testing of nasopharyngeal samples is the most sensitive and preferred test.

The white blood cell count is usually between 15,000 and 20,000/mcL (15 and 20 × 109/L) but may be normal or as high as 60,000/mcL (60 × 109/L), 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. Oxygen 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 weeks 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 orally every 6 hours (maximum 2 g/day) for 14 days

  • Azithromycin 10 to 12 mg/kg orally once a day for 5 days

Trimethoprim/sulfamethoxazole may be substituted in patients ≥ 2 months 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 ages 2, 4, and 6 months; boosters are given at 15 to 18 months and at 4 to 6 years.

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 hours

  • Collapse or shock within 48 hours

  • Fever ≥ 40.5° C within 48 hours

  • 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, which is the currently available preparation, is better tolerated than the previously used vaccine, which contains numerous cell components.

Neither vaccination nor natural disease confers lifelong protective immunity against pertussis or reinfection. Immunity tends to wane 5 to 10 years 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) is recommended for adolescents at age 11 or 12 years and for adults who have never received Tdap; it also should be given during each pregnancy after 20 weeks gestation (preferably at 27 to 36 weeks 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 years. Passive immunization is unreliable and is not recommended.

Close contacts < 7 years who have had < 4 doses of vaccine should be vaccinated.

Postexposure prophylaxis

Postexposure antibiotics should be given to household contacts within 21 days of the onset of cough in the index patient, whether they have been vaccinated or not.

Postexposure antibiotics should also be given to the following high-risk people within 21 days of exposure, whether they have been vaccinated or not:

  • Infants < 12 months

  • Women in the 3rd trimester of pregnancy

  • All people with health conditions potentially exacerbated by pertussis infection (eg, immunodeficiency, moderate to severe asthma, chronic lung disease)

  • People who have close contact with infants < 12 months, pregnant women, or patients with conditions that may result in severe illness or complications

  • All people in high-risk settings that include infants < 12 months or women in the 3rd trimester of pregnancy (eg, child care centers, maternity wards, neonatal intensive care units)

These people should be given a 7- to 14-day course of oral erythromycin 500 mg 4 times a day or 10 to 12.5 mg/kg 4 times a day. Alternative antibiotics include clarithromycin and azithromycin. For infants < 1 month, azithromycin is preferred for postexposure prophylaxis.

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 months.

  • A catarrhal stage with upper respiratory infection 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 weeks, but cough may continue for months.

  • Diagnose using polymerase chain reaction 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.

More Information

Drugs Mentioned In This Article

Drug Name Select Trade
BIAXIN
No US brand name
ERY-TAB, ERYTHROCIN
ZITHROMAX
Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version
Professionals also read

Also of Interest

Videos

View All
Overview of Lyme Disease
Video
Overview of Lyme Disease
3D Models
View All
SARS-CoV-2
3D Model
SARS-CoV-2

SOCIAL MEDIA

TOP