Basics
Description
Pertussis (whooping cough), classically caused by Bordetella pertussis, is a protracted illness characterized by spasms of cough.
Epidemiology
- Pertussis is one of the most highly communicable diseases with attack rates close to 100% in susceptible individuals exposed at close range.
- Humans are the only hosts of B. pertussis.
- Route of spread is via large aerosolized respiratory droplets.
- Spread most commonly occurs during the catarrhal stage and first 2 weeks of cough onset.
- Incubation period 5 " 21 days.
- Pertussis occurs with seasonal peaks (late summer-autumn) and 3 " 5-year cycles of increased incidence of disease.
- Adolescents and adults serve as major reservoirs and source of pertussis for infants.
Incidence
- Pertussis infection rates have steadily risen since the early 1980s.
- This is due to the combination of imperfect vaccines, waning immunity, incomplete vaccination, low transplacental protection for infants, and increased detection and reporting.
- Infants younger than 2 months of age have the highest age-related incidence.
- Rates in adolescents have been steadily increasing and now approach rates in infants.
- Studies have indicated that 10 " 30% of adolescents and young adults with prolonged cough have pertussis.
General Prevention
- Infection control
- Isolation of hospitalized patient: droplet precautions for 5 days after starting appropriate antimicrobial therapy or for 3 weeks after the onset of cough, if antibiotics were not given
- Care of exposed people: Exposed individuals (all household contacts, other close contacts, other children in child care) should receive chemoprophylaxis (same agents and doses as treatment; see the following discussion) to limit secondary transmission, regardless of immunization status. Immunization should be given to all unimmunized and underimmunized children and to adolescents and adults who have not yet received the Tdap booster vaccination.
- Immunizations
- All pertussis vaccines available in the United States are acellular vaccines in combination with diphtheria and tetanus toxoids.
- Universal immunization of all children <7 years of age with DTaP vaccine is recommended as per CDC and AAP guidelines.
- Undervaccinated children ages 7 " 10 years, all adolescents ages 11 " 18 years, adults ages 19 " 64 years, as well as certain adults ages 65 years and older should receive a single dose of Tdap vaccine to help control the rate of infection in infants and young children.
Pathophysiology
- Tropism and replication are limited to the ciliated epithelium of the respiratory tract.
- Biologically active substances such as pertussis toxin (PT), filamentous hemagglutinin, tracheal cytotoxin, adenylate cyclase, and pertactin are responsible for virulence of the organism, including attachment, ciliostasis, impaired leukocyte function, and local epithelial damage.
Etiology
- B. pertussis, a small, nonmotile, fastidious, gram-negative coccobacillus, causes classic pertussis.
- Bordetella parapertussis causes a less protracted cough illness.
Diagnosis
History
- History of a cough illness in other family members, including older siblings, parents, and grandparents, is important to elicit.
- 3 clinical stages
- Catarrhal stage (1 " 2 weeks) with symptoms of an upper respiratory infection
- Paroxysmal stage ( ≥2 " 4 weeks) characterized by paroxysmal cough with increased severity and frequency producing the characteristic whoop during the sudden forceful inspiratory phase; posttussive vomiting is also observed during this stage.
- The convalescent stage begins and lasts 1 " 2 weeks, but cough can persist for several months. In the adolescent or adult, long-standing cough of 2 " 3 weeks is the hallmark symptom. Most patients report a paroxysmal or staccato quality to the cough.
- Apnea is a common manifestation in infants <6 months. The characteristic whoop is typically absent. Short catarrhal stage, gasping, and choking are other manifestations in young infants.
- History of fever is typically absent.
Physical Exam
- Normal physical examination between paroxysms is supportive of the diagnosis.
- Conjunctival hemorrhage and petechiae on the upper body may be present.
- Cyanosis, apnea, and bradycardia can be observed during the paroxysmal stage in young infants.
- Fever and signs of lower respiratory tract disease are uncommon.
Diagnostic Tests & Interpretation
Lab
- CBC
- Leukocytosis (15,000 " 100,000 cells/mm3 with predominant lymphocytosis is commonly observed at the end of the catarrhal stage and throughout the paroxysmal stage of illness in infants and children; not commonly observed in adolescents and adult
- Culture of B. pertussis
- Achieved using calcium alginate or Dacron swabs of the nasopharynx and plated onto selective media such as Regan-Lowe and incubated for 10 days
- Most frequently successful during the catarrhal or early paroxysmal stages and is rarely found beyond the 3rd week of illness
- Specificity 100%; overall sensitivity is 60 " 70% but can be lower in previously vaccinated individuals if antibiotics have already been given or if beyond the 3rd week of illness.
- Polymerase chain reaction (PCR)
- Increasingly used; higher sensitivity and more rapid diagnosis than culture in the detection of B. pertussis from nasopharyngeal specimens
- There is no FDA-licensed PCR test available, and there are no standardized protocols or reagents.
- Direct immunofluorescent assays (DFA) of nasopharyngeal specimens are no longer recommended for the diagnosis of pertussis.
- Serology
- Can be helpful later in the course of the illness
- No commercially available FDA-approved test available and difficult to interpret in previously immunized individuals
- In the absence of recent immunization, an elevated serum IgG antibody to PT after 2 weeks of onset of cough is suggestive of recent infection. An increasing titer or a single IgG anti-PT value of approximately 100 IU/mL or greater can be used for diagnosis.
Imaging
Chest radiograph: may reveal perihilar infiltrates, interstitial edema, and atelectasis
Differential Diagnosis
- B. parapertussis
- Adenoviruses
- Mycoplasma pneumoniae
- Chlamydia trachomatis
- Bronchiolitis
- Bacterial pneumonia
- Cystic fibrosis
- Tuberculosis
- Foreign body aspiration
- Reactive airway disease
Treatment
Medication
- Azithromycin (PO)
- 10 mg/kg as a single dose on day 1, then 5 mg/kg/24 h as a single daily dose on days 2 " 5 is recommended for ages ≥6 months.
- For infants <6 months of age, dosage is 10 mg/kg/24 h as a single daily dose for 5 days.
- For adolescents and adults, dosage is 500 mg as a single dose on day 1, followed by 250 mg as a single daily dose on days 2 " 5.
- Erythromycin PO (40 mg/kg/24 h) in 4 doses for 14 days
- Erythromycin in infants <4 weeks of age is associated with hypertrophic pyloric stenosis. Thus, azithromycin is the drug of choice for treatment or prophylaxis of pertussis in that age group.
- Clarithromycin PO (15 mg/kg/24 h divided b.i.d for 7 days) can be used in children ≥1 month of age.
- Trimethoprim/sulfamethoxazole in children ≥2 months of age, is an alternative agent, although its efficacy is unproven.
General Measures
- Patients with more severe disease manifestations (apnea, cyanosis, feeding difficulties) or other complications require hospitalization for supportive care:
- Infants <6 months of age may develop apnea from fatigue secondary to excessive coughing. They need close observation, preferably in the hospital.
- Antibiotics have little effect on the clinical course unless begun early in the disease process (catarrhal phase) but should always be given to prevent spread of the infection.
Inpatient Considerations
Admission Criteria
- Young infant (<6 months of age) with concern for apnea or fatigue with coughing
- Patients with severe disease manifestations or complications
Discharge Criteria
- No evidence of cardiorespiratory instability
- Able to self-recover from coughing spells
Ongoing Care
Follow-up Recommendations
The paroxysmal stage can last up to 4 weeks and the convalescent stage up to several months.
Prognosis
Directly related to patient age
- Highest mortality is observed in infants <6 months of age, with a 0.5 " 1% risk of death.
- In the older child, prognosis is good.
Complications
- The complications of pertussis are more likely to occur in infants <6 months of age:
- Apnea
- Pneumonia, which may be primary or secondary to viruses (adenovirus, respiratory syncytial virus) or bacteria (Streptococcus pneumoniae, Staphylococcus aureus), occurs in 13 " 25%; the presence of fever or respiratory symptoms in between cough episodes should raise the possibility of secondary bacterial pneumonia.
- Other pulmonary complications include atelectasis, pneumothorax, pneumomediastinum, and subcutaneous emphysema.
- Seizures (2%) and encephalopathy (0.5%) have also been observed in infants with pertussis.
- Complications of pertussis in adolescents and adults include cough syncope, incontinence, rib fractures, and pneumonia.
Additional Reading
- American Academy of Pediatrics. Pertussis (whooping cough). In: Pickering LK, Baker CJ, Kimberlin DW, et al, eds. Red Book: 2012 Report of the Committee on Infectious Diseases. 29th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2012:553 " 566.
- Centers for Disease Control and Prevention. Updated recommendations for use of tetanus toxoid, reduced diphtheria toxoid and acellular pertussis (Tdap) vaccine from the Advisory Committee on Immunization Practices, 2010. MMWR Morb Mortal Wkly Rep. 2011;60(1):13 " 15. [View Abstract]
- Cornia PB, Hersh AL, Lipsky BA. Does this coughing adolescent or adult patient have pertussis? JAMA. 2010;304(8):890 " 896. [View Abstract]
- Klein NP, Bartlett J, Rowhani-Rahbar A, et al. Waning protection after fifth dose of pertussis vaccine in children. N Engl J Med. 2012;367(11):1012 " 1019. [View Abstract]
- Murray EL, Nieves D, Bradley JS, et al. Characteristics of severe Bordetella pertussis infection among infants ≤90 days of age admitted to pediatric intensive care units-Southern California, September 2009 " June 2011. J Pediatr Inf Dis Soc. 2013;2:1 " 6.
- Tiwari T, Murphy TV, Moran J. Recommended antimicrobial agents for the treatment and postexposure prophylaxis of pertussis: 2005 CDC guidelines. MMWR Recomm Rep. 2005;54(RR-14):1 " 16. [View Abstract]
Codes
ICD09
- 033.9 Whooping cough, unspecified organism
- 033.0 Whooping cough due to bordetella pertussis B. pertussis
- 484.3 Pneumonia in whooping cough
- 033.1 Whooping cough due to bordetella parapertussis B. parapertussis
ICD10
- A37.90 Whooping cough, unspecified species without pneumonia
- A37.00 Whooping cough due to Bordetella pertussis without pneumonia
- A37.01 Whooping cough due to Bordetella pertussis with pneumonia
- A37.10 Whooping cough due to Bordetella parapertussis w/o pneumonia
- A37.11 Whooping cough due to Bordetella parapertussis w pneumonia
SNOMED
- 27836007 Pertussis (disorder)
- 77116006 Infection due to Bordetella parapertussis
- 59475000 Pneumonia in pertussis (disorder)
FAQ
- Q: Why is the transmission of pertussis difficult to control in the young infant?
- A: Unfortunately, many physicians do not consider pertussis in adolescents or adults because the symptoms can be nonspecific and often are not severe. They also assume that childhood immunization will protect adults against pertussis. Therefore, delays in antimicrobial treatment are common in adults, owing to the lack of index of suspicion of pertussis by their providers. Finally, there was not a universal recommendation for adolescents and adults to receive pertussis boosters until 2005, even though the immunity protection by pertussis vaccination is limited. It is largely adolescents and adults with pertussis who then spread the disease to young infants and children.
- Q: What is the best way to diagnose pertussis in the young infant?
- A: The diagnosis can be made clinically but requires a high index of suspicion. The diagnosis should be considered based on a history of severe cough in any young infant. At the time of presentation, infants usually appear well and have a normal exam. So, the history provided by the parents of the paroxysmal and severe nature of the course, often associated with gagging, posttussive emesis, and exhaustion, should be taken seriously.