Whooping Cough: Symptoms, Causes, and Treatment

Overview

Whooping cough is caused by Bordetella pertussis, a gram-negative bacterium that specifically targets the respiratory tract. The bacterium produces toxins that damage the ciliated epithelium of the respiratory tract, leading to inflammation and the characteristic persistent cough. The disease progresses through three distinct stages: the catarrhal stage (resembling a cold), the paroxysmal stage (severe coughing fits), and the convalescent stage (gradual recovery).

Before the introduction of the pertussis vaccine in the 1940s, whooping cough was a leading cause of childhood mortality, killing approximately 9,000 people annually in the United States, mostly infants and young children. The widespread use of vaccines has reduced the incidence by more than 99%, but the disease has not been eliminated. In recent years, there has been a resurgence of whooping cough cases, partly due to waning immunity in adolescents and adults, and incomplete vaccination coverage.

The incubation period for whooping cough is typically 7-20 days but can range from 4-42 days. Patients are most contagious during the early catarrhal stage when symptoms resemble a common cold. The disease duration can extend for weeks or months, earning it the nickname "100-day cough." While the illness can be mild in vaccinated individuals, it can be severe and life-threatening in unvaccinated infants and individuals with compromised immune systems.

Symptoms

Whooping cough symptoms develop in three characteristic stages, each lasting several weeks. The progression and severity of symptoms can vary based on age, vaccination status, and overall health.

Stage 1: Catarrhal Stage (1-2 weeks)

Low-grade fever (usually less than 101°F)
Nasal congestion - runny or stuffy nose
Sore throat - mild throat irritation
Sneezing and watery eyes
Mild, dry cough that gradually worsens
General malaise and fatigue
Loss of appetite

Stage 2: Paroxysmal Stage (2-6 weeks)

Severe coughing fits (paroxysms) lasting 1-6 minutes
Characteristic "whoop" sound when gasping for air between coughs
Face turning red or blue (cyanosis) during coughing fits
Vomiting - often triggered by severe coughing
Exhaustion after coughing episodes
Difficulty eating, drinking, or sleeping
Thick, sticky mucus production
Brief periods of shortness of breath

Stage 3: Convalescent Stage (weeks to months)

Gradual decrease in cough frequency and severity
Coughing fits may return with respiratory infections
Slow return to normal energy levels
Possible persistent mild cough for weeks or months
Increased susceptibility to other respiratory infections

Symptoms in Infants (Under 6 months)

Apnea (stopping breathing) episodes
Difficulty feeding and poor weight gain
Seizures from lack of oxygen
Weak or absent "whoop" sound
Bradycardia (slow heart rate)
Lethargy and reduced responsiveness
Pneumonia development

Symptoms in Adolescents and Adults

Prolonged cough lasting weeks or months
Less pronounced or absent "whoop"
Sleep disruption due to nighttime coughing
Rib pain or fractures from severe coughing
Urinary incontinence during coughing fits
Subconjunctival hemorrhages (broken blood vessels in eyes)

Complications and Warning Signs

Pneumonia (most common complication)
Seizures from decreased oxygen levels
Brain damage from hypoxia
Weight loss and dehydration
Hernias from forceful coughing
Middle ear infections
Death (rare, mainly in infants under 3 months)

Causes

Whooping cough is caused by infection with Bordetella pertussis, a highly specialized bacterial pathogen that exclusively infects humans. Understanding how the infection spreads and develops helps in prevention and early treatment.

Bacterial Pathogen

Bordetella pertussis

Type: Gram-negative, aerobic coccobacillus
Specificity: Exclusively human pathogen
Virulence factors: Pertussis toxin, adenylyl cyclase toxin, filamentous hemagglutinin
Target: Ciliated epithelial cells of respiratory tract

Transmission Mechanisms

Airborne Droplet Transmission

Primary route: Respiratory droplets from coughing, sneezing
Droplet size: Small particles remain airborne for extended periods
Range: Can spread up to 6 feet from infected person
Peak infectivity: During catarrhal stage (first 1-2 weeks)

Direct Contact Transmission

Close contact with infected respiratory secretions
Sharing eating utensils, cups, or personal items
Kissing or intimate contact with infected persons
Contaminated surfaces (less common, short survival time)

Pathophysiology

Initial Attachment

Target cells: Ciliated epithelial cells in upper respiratory tract
Attachment factors: Filamentous hemagglutinin, pertactin
Location: Nasal cavity, throat, trachea, bronchi

Toxin Production

Pertussis toxin: Causes systemic effects, lymphocytosis
Adenylyl cyclase toxin: Impairs immune cell function
Tracheal cytotoxin: Damages ciliated epithelium
Dermonecrotic toxin: Causes local tissue damage

Respiratory Tract Damage

Destruction of ciliated epithelium
Loss of normal mucus clearance
Accumulation of thick, tenacious secretions
Airway inflammation and hyperreactivity
Secondary bacterial infections

Related Bordetella Species

Bordetella parapertussis: Causes milder pertussis-like illness
Bordetella holmesii: Rarely causes pertussis-like symptoms
Bordetella bronchiseptica: Mainly affects animals, rarely humans

Environmental Factors

Seasonal variation: Higher incidence in late summer and fall
Crowded conditions: Schools, daycare centers, households
Indoor environments: Poor ventilation increases transmission risk
Climate: Dry air may increase susceptibility

Risk Factors

Several factors increase the risk of contracting whooping cough or developing severe complications. Understanding these risk factors is crucial for prevention and identifying high-risk individuals who need prompt treatment.

Vaccination-Related Risk Factors

Unvaccinated status: Highest risk for severe disease
Incomplete vaccination series: Reduced protection, especially in children
Waning immunity: Protection decreases 5-10 years after vaccination
Vaccine failure: Rare but possible, particularly with acellular vaccines
Delayed vaccination: Infants not yet fully vaccinated

Age-Related Risk Factors

Infants under 6 months: Highest risk for severe complications and death
Infants under 3 months: Most vulnerable, often require hospitalization
Adolescents (11-18 years): Waning immunity from childhood vaccines
Adults over 65: Age-related immune system decline
Pregnant women: Risk of severe disease and transmission to newborn

Exposure Risk Factors

Household contact: Living with infected person
Healthcare workers: Occupational exposure to patients
School attendance: Close contact in classroom settings
Daycare attendance: Young children in group settings
Community outbreaks: Living in areas with current outbreaks

Medical Risk Factors

Immunocompromised conditions:
- HIV/AIDS
- Cancer patients receiving chemotherapy
- Organ transplant recipients
- Chronic corticosteroid use
Chronic respiratory conditions:
- Asthma
- Chronic obstructive pulmonary disease
- Cystic fibrosis
- Bronchopulmonary dysplasia
Cardiovascular disease: Increased risk of complications
Diabetes mellitus: Impaired immune function

Social and Environmental Risk Factors

Crowded living conditions: Increased transmission risk
Poor ventilation: Indoor environments with limited air circulation
Low socioeconomic status: Limited access to healthcare and vaccination
Geographic factors: Areas with low vaccination coverage
Travel: Visiting countries with high pertussis prevalence

Pregnancy-Specific Risk Factors

Unvaccinated during pregnancy: Risk to mother and baby
Third trimester: Critical period for maternal vaccination
Preterm delivery: Premature infants at higher risk
Low birth weight: Increased susceptibility to severe disease

Protective Factors

Up-to-date vaccination: Significantly reduces risk and severity
Maternal antibodies: Provide protection to newborns for first few months
Previous infection: Natural immunity (though can still be reinfected)
Good hygiene practices: Hand washing, covering coughs
Avoiding sick contacts: Isolation during infectious period

High-Risk Groups Requiring Special Attention

Infants under 12 months of age
Pregnant women (especially third trimester)
Healthcare workers
Childcare providers
People with chronic medical conditions
Close contacts of infants

Diagnosis

Diagnosing whooping cough can be challenging, especially in the early stages when symptoms resemble a common cold. Accurate diagnosis requires a combination of clinical assessment, laboratory testing, and epidemiological factors.

Clinical Assessment

Medical History

Symptom progression: Three-stage pattern characteristic of pertussis
Vaccination history: Number and timing of pertussis vaccines
Exposure history: Contact with confirmed or suspected cases
Travel history: Recent travel to areas with outbreaks
Duration of illness: Prolonged cough lasting weeks
Response to treatments: Lack of improvement with typical cough medications

Physical Examination

Observation of coughing fits: Paroxysmal coughing with characteristic whoop
Post-cough vomiting: Common finding during examination
Cyanosis: Blue discoloration during coughing episodes
Lymphadenopathy: Swollen lymph nodes may be present
Lung examination: Usually normal between coughing fits
Signs of complications: Pneumonia, respiratory distress

Laboratory Diagnosis

PCR Testing (Polymerase Chain Reaction)

Gold standard: Most sensitive and specific test
Specimen: Nasopharyngeal swab or aspirate
Timing: Best within first 3 weeks of symptom onset
Results: Available within 24-48 hours
Advantages: High sensitivity and specificity

Bacterial Culture

Specificity: 100% specific but less sensitive than PCR
Timing: Best within first 2 weeks of illness
Results: Takes 3-7 days for growth
Advantages: Allows antibiotic sensitivity testing
Limitations: Slow growth, special media required

Serology (Antibody Testing)

IgG antibodies: Indicates recent infection or vaccination
Timing: Most useful 2-8 weeks after symptom onset
Limitations: Cannot distinguish infection from vaccination
Use: Mainly for epidemiological studies

Supporting Laboratory Tests

Complete Blood Count

Lymphocytosis: Characteristic finding, especially in infants
White blood cell count: Often elevated (15,000-100,000/μL)
Lymphocyte percentage: Often >60% of total WBC

Chest X-ray

Primary purpose: Detect pneumonia complications
Findings: Usually normal unless complications present
Pneumonia pattern: Patchy infiltrates if present

Specimen Collection

Nasopharyngeal Sampling

Preferred method: Flexible Dacron or polyester swab
Technique: Insert swab through nostril to posterior nasopharynx
Duration: Leave in place for 15-30 seconds
Transport: Special transport medium for culture

Clinical Case Definitions

Confirmed Case

Laboratory confirmation (PCR or culture positive)
Clinical symptoms compatible with pertussis

Probable Case

Clinical symptoms compatible with pertussis AND
Epidemiologic linkage to confirmed case OR
Positive serology (in appropriate clinical context)

Suspected Case

Acute cough illness lasting ≥2 weeks
Paroxysmal cough, inspiratory whoop, or post-cough vomiting
No other apparent cause

Differential Diagnosis

Viral respiratory infections: RSV, parainfluenza, influenza
Bacterial pneumonia: Mycoplasma, Chlamydia pneumoniae
Asthma exacerbation: Especially in children with history
Gastroesophageal reflux: Chronic cough in infants
Foreign body aspiration: Sudden onset cough in young children
Tuberculosis: Chronic cough with systemic symptoms
Other Bordetella species: B. parapertussis, B. holmesii

Challenges in Diagnosis

Early stages: Symptoms mimic common cold
Atypical presentations: Especially in vaccinated individuals
Late presentation: Decreased bacterial shedding after 3 weeks
Antibiotic treatment: May affect culture and PCR results
Age variations: Different presentations in different age groups

Treatment Options

Treatment of whooping cough focuses on antibiotic therapy to reduce transmission and supportive care to manage symptoms. Early treatment is most effective, though antibiotics may have limited impact on symptoms if started after the catarrhal stage.

Antibiotic Treatment

First-Line Antibiotics

Azithromycin (Preferred)

Adults: 500 mg on day 1, then 250 mg daily for 4 days
Children ≥6 months: 10 mg/kg on day 1, then 5 mg/kg daily for 4 days
Infants <6 months: 10 mg/kg daily for 5 days
Advantages: Short course, good compliance

Clarithromycin

Adults: 500 mg twice daily for 7 days
Children: 15 mg/kg/day divided twice daily for 7 days
Maximum dose: 1 gram per day

Erythromycin

Adults: 500 mg four times daily for 14 days
Children: 40-50 mg/kg/day divided four times daily for 14 days
Note: Higher side effect profile, especially GI upset

Alternative Antibiotics

Trimethoprim-Sulfamethoxazole

Adults: 160/800 mg twice daily for 14 days
Children ≥2 months: 8/40 mg/kg/day divided twice daily for 14 days
Use: For patients allergic to macrolides

Treatment Goals and Timing

Primary goal: Reduce transmission to others
Secondary goal: Reduce symptom duration and severity
Optimal timing: Within 3 weeks of symptom onset
Late treatment: May not affect symptoms but reduces transmission

Supportive Care

General Measures

Rest: Adequate sleep and reduced activity
Hydration: Maintain fluid intake, especially after vomiting
Nutrition: Small, frequent meals to prevent vomiting
Humidity: Cool mist humidifier may help with cough
Avoidance: Smoke, strong odors, dust that may trigger coughing

Symptomatic Treatment

Cough suppressants: Generally not recommended, may be harmful
Bronchodilators: Limited evidence, may help in some patients
Corticosteroids: Not routinely recommended, limited evidence
Expectorants: No proven benefit

Hospitalization Criteria

Indications for Hospitalization

Age: All infants <6 months, consider for <12 months
Severe respiratory distress: Cyanosis, apnea, hypoxemia
Complications: Pneumonia, seizures, encephalopathy
Feeding difficulties: Inability to maintain hydration/nutrition
Social factors: Inability to care for patient at home

Hospital Management

Monitoring: Continuous cardiorespiratory monitoring
Oxygen therapy: If hypoxemic or cyanotic
Suctioning: Gentle removal of thick secretions
Feeding support: IV fluids or nasogastric feeding if needed
Isolation: Droplet precautions until 5 days of appropriate antibiotics

Treatment of Complications

Pneumonia

Bacterial pneumonia: Additional antibiotics targeting S. pneumoniae, S. aureus
Supportive care: Oxygen, respiratory support as needed
Monitoring: Close observation for respiratory failure

Seizures

Immediate management: Airway protection, oxygen
Anticonvulsants: If prolonged or recurrent
Investigation: Rule out other causes (hypoglycemia, electrolyte abnormalities)

Special Populations

Pregnant Women

Safe antibiotics: Azithromycin, erythromycin
Avoid: Clarithromycin (category C)
Monitoring: Watch for complications, preterm labor

Immunocompromised Patients

Prolonged treatment: May need longer antibiotic courses
Close monitoring: Higher risk of complications
Supportive care: More aggressive supportive measures

Post-Exposure Prophylaxis

Indications

Close contacts of confirmed cases
High-risk individuals (infants, pregnant women, immunocompromised)
Healthcare workers with unprotected exposure

Prophylaxis Regimens

Same antibiotics and doses as treatment
Timing: Most effective within 21 days of exposure
Duration: Usually same as treatment duration

Follow-up and Monitoring

Clinical response: Monitor for symptom improvement
Complications: Watch for development of pneumonia, other complications
Clearance: Consider repeat testing in high-risk situations
Contact tracing: Identify and treat close contacts

Prevention

Prevention of whooping cough relies primarily on vaccination, which is the most effective way to prevent the disease. Additional measures include good hygiene practices, isolation of infected individuals, and post-exposure prophylaxis for high-risk contacts.

Vaccination

Childhood Vaccination Schedule (DTaP)

Primary series: 2, 4, and 6 months of age
Fourth dose: 15-18 months of age
Fifth dose: 4-6 years of age (before school entry)
Vaccine type: DTaP (diphtheria, tetanus, acellular pertussis)
Protection: High initial protection (>95%) that wanes over time

Adolescent and Adult Vaccination (Tdap)

Adolescent booster: Single dose at 11-12 years of age
Adult booster: Single dose for adults who haven't received Tdap
Subsequent boosters: Td (tetanus-diphtheria) every 10 years
Special populations: Healthcare workers, childcare providers

Pregnancy Vaccination

Timing: 27-36 weeks of pregnancy (preferably 27-32 weeks)
Every pregnancy: Recommended for each pregnancy
Benefits: Maternal antibodies protect newborn for first 2-3 months
Safety: Safe for mother and baby

Special Situations

Healthcare workers: Tdap if not previously received
New parents and caregivers: Tdap before contact with infants
Immunocompromised: Follow standard schedule unless contraindicated
Wound management: Tdap if >5 years since last tetanus-containing vaccine

Hygiene and Infection Control

Personal Hygiene

Hand hygiene: Frequent hand washing with soap and water
Alcohol-based sanitizer: When soap and water unavailable
Respiratory etiquette: Cover coughs and sneezes with elbow or tissue
Tissue disposal: Immediate disposal and hand hygiene
Avoid touching face: Especially nose, mouth, and eyes

Environmental Measures

Ventilation: Ensure good air circulation in living spaces
Surface cleaning: Regular disinfection of frequently touched surfaces
Avoid sharing: Personal items, eating utensils, drinks
Crowded spaces: Avoid when possible during outbreaks

Isolation and Quarantine

Infected Individuals

Isolation period: Until 5 days of appropriate antibiotic treatment
If untreated: Isolate for 3 weeks from cough onset
School/work exclusion: During infectious period
Mask wearing: When around others, especially vulnerable populations

Contact Management

Identification: Close contacts defined as face-to-face contact within 3 feet
Monitoring: Watch for symptoms for 21 days
Prophylaxis: Antibiotics for high-risk contacts
Vaccination: Update vaccines as appropriate

Community Prevention

Outbreak Control

Case reporting: Prompt notification to public health authorities
Contact tracing: Identify and manage exposed individuals
School closures: If necessary to control outbreaks
Public education: Information about symptoms and prevention

High-Risk Settings

Healthcare facilities: Enhanced infection control measures
Schools and daycares: Exclusion policies for suspected cases
Maternity units: Screening and isolation protocols
Long-term care facilities: Vaccination and monitoring programs

Special Populations

Protecting Infants

Maternal vaccination: During pregnancy to provide passive immunity
Cocooning strategy: Vaccinate close contacts of newborns
Limited exposure: Minimize contact with large groups
Prompt vaccination: Start infant series at 2 months

Healthcare Worker Protection

Vaccination requirements: Up-to-date Tdap vaccination
Infection control training: Proper use of personal protective equipment
Screening programs: Regular health assessments
Post-exposure management: Prompt evaluation and prophylaxis

Travel Considerations

Pre-travel vaccination: Ensure up-to-date vaccines
High-risk destinations: Areas with current outbreaks
Pregnant travelers: Special precautions and medical consultation
Post-travel monitoring: Watch for symptoms after return

Public Health Measures

Surveillance systems: Monitoring disease trends
Vaccination programs: Maintaining high coverage rates
Education campaigns: Public awareness about vaccination importance
Research: Vaccine development and effectiveness studies

When to See a Doctor

Seek immediate emergency care for:

Difficulty breathing or shortness of breath
Blue coloration of lips or face (cyanosis)
Stopping breathing during coughing fits (apnea)
Seizures or loss of consciousness
Signs of severe dehydration
Inability to keep fluids down due to persistent vomiting

Call your healthcare provider urgently for:

Persistent cough lasting more than 2 weeks
Characteristic "whooping" sound after coughing fits
Coughing fits that cause vomiting
Fever with prolonged cough
Exposure to confirmed whooping cough case
Symptoms in infants under 6 months old

Schedule an appointment for:

Persistent cold symptoms lasting more than 7-10 days
Nasal congestion with worsening cough
Sore throat with prolonged cough
Questions about vaccination status
Pregnancy and concerns about whooping cough exposure
Need for post-exposure prophylaxis after contact with infected person

Special considerations for infants:

Any respiratory symptoms in babies under 3 months
Feeding difficulties or poor weight gain
Changes in crying pattern or lethargy
Any cough in unvaccinated infants

Related Conditions

References

Centers for Disease Control and Prevention. Pertussis (Whooping Cough): Clinical Features. Atlanta, GA: CDC; 2017.
American Academy of Pediatrics. Pertussis (Whooping Cough). In: Kimberlin DW, Brady MT, Jackson MA, Long SS, eds. Red Book: 2018 Report of the Committee on Infectious Diseases. 31st ed. Itasca, IL: American Academy of Pediatrics; 2018:620-634.
Mattoo S, Cherry JD. Molecular pathogenesis, epidemiology, and clinical manifestations of respiratory infections due to Bordetella pertussis and other Bordetella subspecies. Clin Microbiol Rev. 2005;18(2):326-382.
World Health Organization. Pertussis vaccines: WHO position paper - August 2015. Wkly Epidemiol Rec. 2015;90(35):433-458.
Bisgard KM, Pascual FB, Ehresmann KR, et al. Infant pertussis: who was the source? Pediatr Infect Dis J. 2004;23(11):985-989.