Whooping Cough

1. See Also
   1. Bacterial Pneumonia
2. Epidemiology
   1. Incidence
      1. U.S. (2012): 41,000 cases/year and 18 deaths (mostly infants)
      2. Worldwide: 30-50 million cases/year with 300,000 deaths/year
   2. Pertussis is a common cause of adult Chronic Cough
      1. Pertussis is responsible for 20% of severe cough in adults and teens >2 weeks presenting to emergency departments
         1. Senzilet (2001) Clin Infect Dis 32:1691-7
      2. Most cases occur in over age 10 years
      3. With waning immunity, teens and adults are reservoir
         1. Immunity wanes by as much as 42% per year since last DTaP
         2. Klein (2012) N Engl J Med 367(11): 1012-9
   3. Infants are infected by adults
      1. Infants account for most of Pertussis-related mortality (especially under age 3 months)
      2. Infant immunity <1 year is incomplete
      3. Infants comprise >50% of all childhood infections
      4. Infection most severe in infants including death
3. Etiologies
   1. Bordetella pertussis
   2. Bordetella parapertussis
4. Pathophysiology
   1. Extremely contagious with 80-100% secondary attack rate in those susceptible
   2. Droplet spread with inhalation into airways
   3. Pertussis releases toxins that damage the respiratory epithelium and result in mucosal injury
   4. Incubation period: 7 to 10 days (incubation may be as long as 3 weeks)
5. Signs and symptoms
   1. Catarrhal Stage (1-2 weeks)
      1. Low grade fever
      2. Malaise
      3. Mild Conjunctivitis
      4. Pharyngitis
      5. Rhinitis
      6. Sneezing
      7. Lacrimation
   2. Paroxysmal Cough Stage (2-4 weeks with peak at 2 weeks)
      1. Infants under age 6 months
         1. Apnea
         2. Persistent cough (not in spasms)
         3. Decreased oral intake
      2. Older infants, children and adults
         1. Gradually progressive cough in spasms to severe coughing fits
            1. Patient feels as if cannot breath during coughing fit
            2. Typically breathing is unencumbered between coughing fits
         2. Inspiratory whoop (not heard in adults)
            1. Occurs when a deep breath is taken against a closed glottis
         3. Post-tussive Emesis
            1. Vomiting may occur with severe cough
         4. Cyanosis following coughing spasms
         5. Associated secondary conditions
            1. Cough Syncope
            2. Cough fracture (Rib Fracture)
            3. Pneuomothorax
            4. Hernia
            5. Rectal Prolapse
   3. Convalescent Stage (1-2 weeks)
      1. Bacteria clear with 3-4 weeks of infection onset
      2. Respiratory epithelium remains damaged following acute infection and prolonged recovery represents healing time
      3. Coughing spasms resolve over 1-3 months ("80 day cough")
6. Signs
   1. Fine rales on Lung Exam
7. Differential Diagnosis
   1. Catarrhal stage
      1. Viral Upper Respiratory Infection (e.g. Adenovirus)
   2. Paroxysmal stage
      1. See Cough Causes
      2. Mycoplasma pneumoniae
      3. Chlamydia pneumoniae
   3. Convalescent stage with persistent cough
      1. See Chronic Cough
      2. Asthma
      3. Gastroesophageal Reflux
      4. Acute Sinusitis with post nasal drainage
8. Labs
   1. See Bordetella Pertussis Test
   2. Complete Blood Count
      1. Leukocytosis from 15,000 to as high as 100,000
      2. Higher White Blood Cell counts are associated with worse prognosis
9. Diagnosis
   1. See Bordetella Pertussis Test
   2. Cough for less than one week is typically of viral origin
      1. Consider Pertussis when cough persists for longer than 2 weeks, especially when worsens over time or
      2. During local outbreaks or known Pertussis contact
   3. Clinical suspicion criteria
      1. Major Criteria: Acute cough for 14 days
      2. Minor criteria (requires one)
         1. Paroxysmal cough
         2. Post-tussive Emesis
         3. Inspiratory Whoop
         4. Pertussis outbreak
10. Management
    1. Pertussis is a clinical diagnosis (see diagnosis above)
    2. Treatment and reporting are based on clinical suspicion
       1. Test and treat empirically at time of testing if clinically suspect
          1. Do not delay antibiotics for test confirmation (test will return about the time a 5 day antibiotic course is completed)
          2. Early treatment has the best efficacy
       2. Quarantine at time of diagnosis for 5 full days on antibiotics or earlier if longer than three weeks since symptom onset
       3. Treat close contacts (asymptomic contacts need not be quarantined)
       4. Report clinically suspected cases before confirmation
    3. Antibiotic dosing
       1. Azithromycin for 5 days
          1. Preferred first line option
          2. Avoid shorter 3 day courses due to lack of supporting evidence
       2. Other Macrolides
          1. Clarithromycin for 14 days
          2. Erythromycin
             1. Child: 40-50 mg/kg/day divided qid for 14 days
             2. Adults: 500 mg PO qid for 14 days
       3. Bactrim (not as effective as Macrolides)
          1. Indicated for Macrolide allergy or GI intolerance
          2. Do not use in pregnancy, Lactation, age <2 months
          3. Dosing
             1. Child: 8 mg/kg Trimethoprim divided bid x14 days
             2. Adult: Bactrim DS one tablet bid for 14 days
             3. Maximum dose: 320/1600 mg TMP/SMX
11. Management: Prevention of spread
    1. Quarantine
       1. Pertussis patients are off work and out of school
       2. May return after 5 days on antibiotics or sooner if 3 weeks after paroxysmal stage ends
    2. Prophyaxis: Treat close contacts with exposure within 3 weeks
       1. Contacts are typically asymptomatic and need not be quarantined
       2. Use same antibiotic course as above
       3. Monitor contacts for 3 weeks for onset of symptoms
12. Prevention
    1. Diphtheria Tetanus Acellular Pertussis Vaccine (DTaP)
       1. Primary Series for 5 doses by age 5 years
    2. Tdap (Boostrix, Adacel)
       1. Pimary series booster at age 11 years old
       2. Adults 18 to 64 years old for Tetanus booster every 10 years (may substitute for any Td dose)
       3. Pregnant women in third trimester (repeat with each pregnancy)
13. Complications (usually limited to infants)
    1. Hospitalization
    2. Superimposed Bacterial Pneumonia
    3. Dehydration
    4. Encephalopathy
    5. Death (rate has been rising for infants)
14. Resources
    1. CDC Pertussis
       1. http://www.cdc.gov/pertussis/
15. References
    1. Coffman (2005) Hospital Physician
    2. Takhar and Herbert in Majoewsky (2013) EM:Rap 13(4): 2-3
    3. Gilbert (2001) Sanford Antimicrobial, p. 25
    4. Birkebaek (1999) Clin Infect Dis 29:1239-42
    5. Gregory (2006) Am Fam Physician 74:420-7