Pertussis is a highly contagious respiratory infection caused by Bordetella pertussis, characterized by a classic triad of paroxysmal cough, inspiratory whoop, and posttussive vomiting. It progresses through three phases (catarrhal → paroxysmal → convalescent) and remains a significant cause of morbidity, particularly in unvaccinated infants and adults with waning immunity. [1-2]
1. History
- Cough characterization: Onset, duration, paroxysmal nature (repetitive vigorous coughs during a single expiration with inability to breathe during spells), nocturnal predominance, triggers [2]
- Posttussive symptoms: Vomiting immediately after coughing, gagging, cyanosis, syncope, urinary incontinence [1]
- Inspiratory whoop: Forceful inspiration producing a whooping sound after a coughing paroxysm [2]
- Timing and progression: Initial 1–2 weeks of nonspecific URI symptoms (catarrhal phase) → paroxysmal cough developing over weeks 2–3 and lasting 2–3 months → gradual resolution (convalescent phase, "100-day cough") [1][3]
- Incubation period: 7–10 days (longer than typical viral URIs at 1–3 days) [1]
- Important negatives: Fever is typically absent (present in only ~12% of adults); its presence argues against pertussis. Asymptomatic between paroxysms [1-3]
- Exposure history: Known contact with a confirmed case, household members with prolonged cough, daycare/school outbreaks [2-3]
- Vaccination history: DTaP/Tdap status, time since last dose (immunity wanes; odds of pertussis increase ~1.33× per year since last dose) [3-4]
2. Alarm Features
- Infants <3 months: Apnea (with or without cyanosis), bradycardia, poor feeding, deceptively well appearance that rapidly deteriorates [5-6]
- Leukocytosis >40,000–50,000/μL (especially with lymphocytosis): Strongly associated with ICU admission and mortality in infants [7-8]
- Cyanosis during or after paroxysms [6][8]
- Pneumonia (5–9% of adults ≥30 years; higher in infants) [1][6]
- Pulmonary hypertension in young infants — a major cause of death in fulminant pertussis [9-10]
- Syncope (~2% of adults), rib fractures (~2%), seizures, encephalopathy [1][11]
- Respiratory failure requiring mechanical ventilation [9][12]
3. Medications
Treatment (primarily to reduce transmission, not to shorten clinical course): [1][3][13]
- Azithromycin (preferred):
- Adults: 500 mg day 1, then 250 mg days 2–5; OR 500 mg daily × 3 days
- Children: 10 mg/kg day 1, then 5 mg/kg days 2–5; OR 10 mg/kg daily × 3 days
- Clarithromycin: 7.5 mg/kg/dose BID × 7 days (adults: 500 mg BID × 7 days) [13]
- Erythromycin: 40–50 mg/kg/day divided QID × 14 days (more GI side effects, less preferred) [13-14]
- TMP-SMX (alternative for macrolide intolerance): 8 mg/kg/day TMP divided BID × 14 days [1][13]
Key medication points
- Antibiotics eradicate the organism but do not alter the clinical course once the paroxysmal phase has begun [3][13]
- Treat within 3 weeks of cough onset to reduce transmission; treatment after 3 weeks generally not recommended (cough is toxin-mediated, not from ongoing infection) [1]
- Exception: Pregnant individuals near term should receive antibiotics up to 6 weeks after cough onset [1]
- Azithromycin is preferred in pregnancy [1]
- No proven benefit from corticosteroids, salbutamol, diphenhydramine, or pertussis immune globulin for symptom control [14]
Contraindicated/Cautions
- Fluoroquinolones: In vitro activity but no clinical data to support use [14]
- Erythromycin estolate: Associated with hepatotoxicity; may not be available [13]
4. Diet
- Hydration: Critical in infants and young children who may become dehydrated from posttussive vomiting and inability to feed [14]
- Small, frequent meals to reduce vomiting triggers
- No specific dietary triggers for pertussis; nutritional support is primarily supportive
5. Review of Systems
- Respiratory: Cough quality, wheezing, dyspnea, apneic episodes, hemoptysis [15]
- GI: Posttussive vomiting, feeding difficulties, weight loss
- Neurologic: Syncope, seizures, headache [11][15]
- GU: Urinary incontinence (approximately one-third of females ≥50 years) [1]
- MSK: Chest/abdominal wall soreness, rib pain [1][3]
- Ophthalmologic: Scleral hemorrhage, subconjunctival hemorrhage [3]
- Constitutional: Malaise, rhinorrhea (catarrhal phase); notably absence of significant fever [1]
6. Collateral History and Family History
- Household contacts: Any family member with prolonged cough illness — the source of pertussis in young infants is most often a family member [5]
- Daycare/school exposure: Known outbreaks or confirmed cases in the community
- Vaccination status of household members and close contacts [3]
- No hereditary predisposition, but household crowding and poor ventilation increase transmission risk [16]
- Pregnancy status: Maternal Tdap vaccination between 27–36 weeks' gestation provides passive immunity to newborns [3]
7. Risk Factors
- Unvaccinated or undervaccinated status — the single most important risk factor [4][16]
- Waning vaccine immunity: Acellular pertussis vaccines provide shorter-duration protection than whole-cell vaccines; immunity wanes significantly within 3–5 years [4][17]
- Age extremes: Infants <3 months (highest morbidity/mortality), elderly ≥65 years [1][6]
- Asthma and COPD: Increased risk of acquisition and more severe disease [1]
- Obesity: Risk factor for acquiring pertussis [1]
- Immunocompromised state and cigarette smoking: Higher risk for severe disease [1]
- Prematurity in infants [8]
- Contact with a confirmed case [16]
8. Differential Diagnosis
- Mycoplasma pneumoniae infection: Prolonged cough, may have fever, younger adults; chest X-ray may show patchy infiltrates [18]
- Chlamydophila pneumoniae: Subacute cough, hoarseness, pharyngitis
- Viral URI / postinfectious cough: Most common cause of prolonged cough; typically self-limited, may have preceding fever [18]
- Asthma / cough-variant asthma: Nocturnal cough, wheezing, response to bronchodilators [18]
- Upper airway cough syndrome (postnasal drip): Throat clearing, nasal congestion [18]
- GERD / laryngopharyngeal reflux: Heartburn, voice changes, worse supine [18]
- ACE inhibitor–induced cough: Dry, nonproductive; resolves with drug discontinuation [18]
- Tuberculosis: Chronic cough, weight loss, night sweats, hemoptysis — especially in endemic areas
- Foreign body aspiration (children): Acute onset, unilateral wheezing [18]
- Protracted bacterial bronchitis (children): Wet cough >4 weeks, responds to antibiotics [19]
Key distinguishing features of pertussis: Paroxysmal cough with posttussive vomiting and inspiratory whoop, absence of fever, and known exposure [1-2][20]
9. Past Medical History
- Prior pertussis infection: May attenuate severity but does not confer lifelong immunity [1]
- Vaccination history: DTaP series completion, Tdap booster timing [3-4]
- Chronic lung disease (asthma, COPD): Increases risk and severity [1]
- Immunodeficiency: Higher risk for severe and prolonged disease
- Pregnancy: Relevant for treatment decisions and neonatal protection [1][3]
10. Physical Exam
- Vital signs: Typically afebrile; tachycardia may occur during paroxysms; oxygen desaturation during coughing spells; bradycardia in infants during paroxysms [1][5]
- General: Patient may appear well between paroxysms ("deceptively well" in infants) [5]
- HEENT: Scleral/subconjunctival hemorrhage, facial plethora/petechiae from coughing [3]
- Lungs: Often clear between paroxysms; may have rhonchi or crackles if pneumonia develops
- Observe a coughing paroxysm if possible: Repetitive staccato coughs on single expiration → inspiratory whoop → posttussive emesis/gagging
- Infants: Apnea, cyanosis, eye bulging, gasping [5]
11. Lab Studies
- Nasopharyngeal PCR (test of choice): Sensitivity 77–97%, specificity 88–97%; optimal within first 4 weeks of cough onset [3]
- Nasopharyngeal culture: 100% specific but sensitivity only 20–80%; best within first 2 weeks; requires special media, results in 7–10 days [1][3]
- Serology (anti-pertussis toxin IgG): Useful 3–12 weeks after symptom onset; not reliable if vaccinated within the past year [3]
- CBC: Leukocytosis with lymphocyte predominance — particularly in infants <3 months where WBC >20,000/μL with >50% lymphocytes is virtually diagnostic [3]
- WBC >40,000/μL: Independent risk factor for ICU admission and death in infants [7][21]
- CRP: May be elevated in severe cases with secondary infection [9]
- CXR: Not routinely needed; obtain if pneumonia suspected
12. Imaging
- Chest X-ray: Not routinely indicated; obtain if concern for pneumonia, respiratory distress, or hypoxia
- Findings when abnormal: Perihilar infiltrates, atelectasis, consolidation (especially in infants) [6]
- "Shaggy heart" sign described in severe infant pertussis
- CT chest: Rarely needed; consider if atypical presentation or concern for alternative diagnosis
- Imaging is unnecessary in uncomplicated pertussis in otherwise healthy adolescents/adults
13. Special Tests
- Targeted singleplex NAAT for B. pertussis: Preferred over syndromic respiratory panels, which may have suboptimal sensitivity for pertussis detection [22]
- Use Dacron or nylon swabs (not cotton — toxic to B. pertussis); specimen must be from posterior nasopharynx, not anterior nares or throat [23]
- Direct fluorescent antibody (DFA): No longer recommended due to poor sensitivity and specificity [3]
- No validated clinical decision rule exists for pertussis diagnosis [3]
- CDC clinical case definition: Cough ≥2 weeks + paroxysmal cough, inspiratory whoop, posttussive emesis, or apnea (infants <1 year) [2-3]
14. ECG
- Not routinely indicated in uncomplicated pertussis
- Consider ECG in patients with:
- Syncope during coughing paroxysms [15]
- Cardiac arrhythmias — reported in ~40% of severe adult cases in one series [15]
- Bradycardia in infants during paroxysms [5]
- Echocardiography in critically ill infants to evaluate for pulmonary hypertension — a major contributor to mortality in fulminant pertussis [9-10]
15. Assessment
Classic three-phase illness: [1][3]
- Catarrhal phase (1–2 weeks): Indistinguishable from viral URI — rhinorrhea, malaise, mild cough, no/low-grade fever
- Paroxysmal phase (2–3 months): Paroxysmal cough, whoop, posttussive vomiting; patient well between episodes
- Convalescent phase (weeks to months): Gradual resolution; "100-day cough"
Atypical presentations: Prior vaccination or infection may attenuate illness — prolonged cough >2 weeks may be the only symptom. Among adults with prolonged cough, 12–32% have pertussis. [1] Infants may present with apnea rather than classic whoop. [5]
Complications: Pneumonia (5–9% in adults ≥30), rib fractures, syncope, urinary incontinence, subconjunctival hemorrhage, pneumothorax, carotid artery dissection, hearing loss. [1][11] In infants: apnea, seizures, encephalopathy, pulmonary hypertension, death. [5][10]
16. Treatment Plan
Initial management
- Droplet precautions until 5 days of appropriate antibiotic therapy completed (or 21 days from cough onset if untreated) [24]
- Empiric antibiotics if clinical suspicion is high — do not wait for test results, especially if contact with high-risk individuals [1]
- Azithromycin is first-line (see dosing above) [1][3][13]
Postexposure prophylaxis (same regimens as treatment): [3][13]
Supportive care
- Hydration and nutrition support, especially in infants with posttussive vomiting [14]
- Supplemental oxygen as needed
- No proven benefit from cough suppressants, corticosteroids, bronchodilators, or pertussis immune globulin [11][14]
Severe/fulminant infant pertussis
- ICU admission, mechanical ventilation, inotropic support [9-10]
- Exchange blood transfusion may be considered for extreme leukocytosis with pulmonary hypertension/cardiogenic shock [9]
Vaccination
- Tdap for all patients ≥11 years who have not received it [3]
- Tdap during each pregnancy at 27–36 weeks' gestation [3]
- Ensure close contacts of infants are up to date [3]
Public health: Pertussis is a reportable disease — notify local health department [24]
17. Disposition
Admission criteria
- All infants <4 months with suspected pertussis (high risk for apnea, respiratory failure) [5][8]
- Respiratory distress, hypoxia, apnea, cyanosis
- Inability to tolerate oral intake / dehydration from posttussive vomiting
- Pneumonia
- WBC >40,000/μL in infants (consider ICU) [7]
- Significant comorbidities (immunocompromised, severe asthma/COPD)
ICU criteria: [8-10]
- Apnea requiring monitoring/intervention
- Respiratory failure
- Pulmonary hypertension
- Hemodynamic instability
- Extreme leukocytosis (>50,000/μL) in infants
Discharge criteria
- Tolerating oral intake
- No apnea or oxygen requirement
- Completed ≥5 days of antibiotics (no longer contagious)
- Reliable follow-up and caregiver education
Most adolescents and adults can be managed as outpatients with oral antibiotics [1]
18. Follow Up / Return Precautions
- Follow-up: Primary care within 1–2 weeks to reassess cough trajectory and confirm test results
- Isolation: Exclude from work/school/daycare until 5 days of antibiotics completed; if untreated, exclude for 21 days from cough onset [24]
- Expected course: Paroxysmal cough may persist for 2–3 months despite appropriate treatment — antibiotics do not shorten the cough [1][3]
- Return immediately for: Apnea, cyanosis, inability to eat/drink, persistent vomiting, syncope, worsening respiratory distress, high fever (suggests secondary infection/pneumonia)
- Counsel: Cough will gradually improve; no effective cough suppressant exists; avoid triggers that provoke paroxysms
- Ensure household contacts receive prophylaxis and vaccination updates [3][13]
- Report to public health for contact tracing and outbreak management [24]
References
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2. Clinically Diagnosing Pertussis-Associated Cough in Adults and Children: CHEST Guideline and Expert Panel Report. — Moore A, Harnden A, Grant CC, Patel S, Irwin RS. Chest. 2019.
3. Pertussis: Common Questions and Answers. — Kline JM, Smith EA, Zavala A. American Family Physician. 2021.
4. Association Between Vaccine Refusal and Vaccine-Preventable Diseases in the United States: A Review of Measles and Pertussis. — Phadke VK, Bednarczyk RA, Salmon DA, Omer SB. The Journal of the American Medical Association. 2016.
5. Pertussis in Young Infants Throughout the World. — Cherry JD. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2016.
6. Clinical Characteristics of 967 Children With Pertussis: A Single-Center Analysis Over an 8-Year Period in Beijing, China. — Kang L, Cui X, Fu J, et al. European Journal of Clinical Microbiology & Infectious Diseases : Official Publication of the European Society of Clinical Microbiology. 2022.
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9. Severe Pertussis Infections in Pediatric Intensive Care Units: A Multicenter Study. — Akçay N, Tosun D, Bingöl İ, et al. S European Journal of Pediatrics. 2025.
10. Fulminant Pertussis: A Multi-Center Study With New Insights Into the Clinico-Pathological Mechanisms. — Sawal M, Cohen M, Irazuzta JE, et al. Pediatric Pulmonology. 2009.
11. Symptomatic Treatment of the Cough in Whooping Cough. — Wang K, Bettiol S, Thompson MJ, et al. The Cochrane Database of Systematic Reviews. 2014.
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13. Antibiotics for Whooping Cough (Pertussis). — Altunaiji S, Kukuruzovic R, Curtis N, Massie J. The Cochrane Database of Systematic Reviews. 2007.
14. Pertussis — Not Just for Kids. — Hewlett EL, Edwards KM. The New England Journal of Medicine. 2005.
15. Whooping Cough in Adults: A Series of Severe Cases. — Zycinska K, Cieplak M, Chmielewska M, et al. Advances in Experimental Medicine and Biology. 2017.
16. Pertussis Outbreak Investigation in Northwest Ethiopia: A Community Based Study. — Yeshanew AG, Lankir D, Wondimu J, Solomon S. PloS One. 2022.
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18. Chronic Cough: Evaluation and Management. — Sonoda K, Nayak R. American Family Physician. 2024.
19. Diagnosis in Children With Prolonged or Recurrent Cough: Findings From the Swiss Paediatric Airway Cohort. — Mallet MC, Elmiger A, Glick S, et al. Pediatric Pulmonology. 2025.
20. Clinical Characteristics of Pertussis-Associated Cough in Adults and Children: A Diagnostic Systematic Review and Meta-Analysis. — Moore A, Ashdown HF, Shinkins B, et al. Chest. 2017.
21. Clinical Characteristics and Mortality Risk Factors Among Hospitalized Infants and Children With Pertussis in China: A Retrospective Study. — Zheng S, Luo F, Su Y, et al. Frontiers in Public Health. 2025.
22. Guide to Utilization of the Microbiology Laboratory for Diagnosis of Infectious Diseases: 2024 Update by the Infectious Diseases Society of America (IDSA) and the American Society for Microbiology (ASM). — Miller JM, Binnicker MJ, Campbell S, et al. Clinical Infectious Diseases : An Official Publication of the Infectious Diseases Society of America. 2024.
23. Does This Coughing Adolescent or Adult Patient Have Pertussis?. — Cornia PB, Hersh AL, Lipsky BA, Newman TB, Gonzales R. The Journal of the American Medical Association. 2010.
24. Prevention of Pertussis, Tetanus, and Diphtheria With Vaccines in the United States: Recommendations of the Advisory Committee on Immunization Practices (ACIP). — Liang JL, Tiwari T, Moro P, et al. MMWR. Recommendations and Reports : Morbidity and Mortality Weekly Report. Recommendations and Reports. 2018.