Whooping Cough: Symptoms, Causes & Treatment Guide

What Is Whooping Cough and What Causes It?

Whooping cough (pertussis) is a highly contagious respiratory infection caused by the bacterium Bordetella pertussis. The bacteria attach to the cilia (tiny hair-like structures) lining the airways and release toxins that damage the respiratory tract, causing intense inflammation and the characteristic severe coughing fits.

Whooping cough, medically known as pertussis, is one of the most contagious respiratory diseases known to medicine. The disease gets its common name from the characteristic "whooping" sound that many patients make when they gasp for air after a severe coughing fit. Before widespread vaccination, whooping cough was a leading cause of childhood illness and death, with hundreds of thousands of cases occurring annually in many countries.

The bacterium Bordetella pertussis is the primary cause of whooping cough, although a related species called Bordetella parapertussis can cause a milder form of the disease. These bacteria are exclusively human pathogens, meaning they only infect humans and cannot survive for long periods outside the human body. The organism produces several toxins and virulence factors that enable it to colonize the respiratory tract and evade the immune system.

When Bordetella pertussis enters the respiratory tract, it attaches to the epithelial cells lining the airways using specialized adhesins. Once attached, the bacteria produce pertussis toxin, which is responsible for many of the disease's systemic effects. This toxin interferes with cell signaling and immune responses, allowing the bacteria to multiply and cause inflammation. The bacteria also produce tracheal cytotoxin, which specifically damages the ciliated cells of the respiratory tract, impairing the natural clearance mechanism that normally removes pathogens and mucus.

How Whooping Cough Spreads

Whooping cough spreads primarily through respiratory droplets when an infected person coughs, sneezes, or even speaks. The bacterium is extremely efficient at transmission, with one infected person capable of spreading the disease to 12-17 susceptible individuals who have close contact with them. This makes it one of the most contagious vaccine-preventable diseases.

The highest risk of transmission occurs during the early stages of illness, particularly during the first two weeks of coughing before the characteristic whooping begins. Many adults and vaccinated individuals may have mild symptoms that resemble a regular cold, unknowingly transmitting the infection to vulnerable contacts such as unvaccinated infants. After appropriate antibiotic treatment for 5 days, infected individuals are generally no longer contagious.

Global Impact and Epidemiology

Despite widespread vaccination programs, whooping cough remains a significant global health concern. The World Health Organization estimates that approximately 16 million cases occur worldwide each year, resulting in about 195,000 deaths. The vast majority of these deaths occur in developing countries among unvaccinated or partially vaccinated infants.

In developed countries with high vaccination rates, whooping cough continues to circulate and periodically causes outbreaks. Several factors contribute to this ongoing transmission: waning immunity from both vaccination and natural infection, improved diagnostic testing leading to better detection, and the inability of current vaccines to prevent bacterial colonization even when they prevent disease. Understanding these factors is crucial for public health strategies aimed at protecting vulnerable populations.

What Are the Symptoms of Whooping Cough?

Whooping cough symptoms progress through three distinct stages: the catarrhal stage (1-2 weeks of cold-like symptoms), the paroxysmal stage (1-6 weeks of severe coughing fits with the characteristic "whoop"), and the convalescent stage (weeks to months of gradual recovery). Infants may not develop the typical whoop and instead may have apnea (breathing pauses) or turn blue.

The clinical presentation of whooping cough is distinct from most other respiratory infections due to its prolonged course and characteristic symptom progression. The disease unfolds in three recognized stages, each with its own symptom profile and level of contagiousness. Understanding these stages is essential for early recognition and appropriate treatment.

Stage 1: Catarrhal Stage (1-2 Weeks)

The initial stage of whooping cough closely resembles a common cold, which is why many cases go unrecognized early on. During this phase, patients typically experience a runny nose, mild cough, low-grade fever (usually below 38.5°C/101°F), and general malaise. The cough is initially mild and nonproductive, giving little indication of the severe illness to come.

Unfortunately, this stage represents the period of highest contagiousness. Patients shed large numbers of bacteria in their respiratory secretions, and because symptoms are mild and nonspecific, they often continue their normal activities, unknowingly exposing others to the infection. This is particularly concerning when exposed individuals include unvaccinated infants or immunocompromised people.

Stage 2: Paroxysmal Stage (1-6 Weeks)

The paroxysmal stage is the hallmark of whooping cough and typically begins 1-2 weeks after initial symptoms. During this phase, patients develop the characteristic severe coughing fits (paroxysms) that give the disease its name. These episodes are sudden, uncontrollable bursts of rapid coughing that can last for several minutes and occur multiple times per day.

The distinctive "whoop" occurs when the patient gasps for air at the end of a coughing paroxysm. As the patient tries to inhale through a narrowed or inflamed airway, air rushing through creates the high-pitched whooping sound. However, it's important to note that not all patients whoop—infants, adults, and vaccinated individuals often have atypical presentations without the characteristic sound.

Additional symptoms during this stage include:

• Post-tussive vomiting: Vomiting immediately after coughing fits is extremely common and can lead to weight loss and dehydration
• Facial color changes: The face may turn red, purple, or blue (cyanosis) during paroxysms due to difficulty breathing
• Extreme exhaustion: Patients often appear exhausted after coughing episodes and may fall asleep immediately
• Subconjunctival hemorrhage: Broken blood vessels in the eyes due to forceful coughing
• Rib fractures: In severe cases, particularly in older adults, the force of coughing can fracture ribs
• Urinary incontinence: Common during severe coughing fits

Stage 3: Convalescent Stage (Weeks to Months)

The convalescent or recovery stage begins when coughing paroxysms gradually decrease in frequency and severity. This stage can last from several weeks to months. While patients are no longer contagious during this phase, they may still experience occasional coughing episodes, particularly when exposed to respiratory irritants, cold air, or other respiratory infections.

A characteristic feature of the convalescent stage is the "recrudescence" phenomenon—temporary return of whooping cough-like symptoms when the patient develops another respiratory infection, even years after the original illness. This occurs because the damage to the respiratory tract takes considerable time to fully heal.

Symptoms in Infants: A Critical Difference

Infants, particularly those under 6 months of age, often present differently from older children and adults. They may not develop the classic whooping sound, making the disease harder to recognize. Instead, the most concerning symptom in infants is apnea—periods where they stop breathing, which can be life-threatening.

Parents and caregivers should watch for: episodes of turning blue or pale, difficulty breathing, becoming limp or unresponsive, poor feeding, and vomiting after feeding. Any of these symptoms in an infant warrants immediate medical evaluation, as whooping cough in this age group can progress rapidly to respiratory failure.

What Are the Complications of Whooping Cough?

Whooping cough complications are most severe in infants and include pneumonia (occurs in 1 in 4 infants with pertussis), seizures, encephalopathy (brain damage), apnea, and death. In older children and adults, complications include rib fractures from coughing, hernia, urinary incontinence, and fainting. Approximately 50% of infants under 1 year require hospitalization.

While whooping cough can cause significant discomfort at any age, the potential for severe and life-threatening complications is highest in infants, particularly those under 6 months of age. Understanding these complications helps parents and caregivers recognize when medical attention is urgently needed.

Complications in Infants

The immature respiratory and immune systems of infants make them particularly vulnerable to severe whooping cough complications. Pneumonia is the most common serious complication, occurring in approximately 25% of infants with whooping cough. This bacterial pneumonia can be caused by the pertussis bacteria itself or by secondary bacterial infections that take advantage of the damaged airways.

Apnea and breathing difficulties pose an immediate life-threatening risk. Unlike older children who may whoop and recover between coughing fits, infants may simply stop breathing. This can lead to hypoxia (low oxygen levels) and, if prolonged, brain damage. Seizures occur in about 1-2% of infant cases and are often related to oxygen deprivation during apnea episodes or to the effects of pertussis toxin on the nervous system.

Encephalopathy, or brain dysfunction, is a rare but devastating complication affecting approximately 0.5% of hospitalized infants with whooping cough. This can result from direct toxin effects, oxygen deprivation, or bleeding within the brain from the force of coughing. The outcome can include permanent neurological damage, developmental delays, or death.

Complications in Adolescents and Adults

While adolescents and adults rarely die from whooping cough, they can experience complications that significantly impact quality of life. The force of severe coughing paroxysms can cause rib fractures, particularly in older adults or those with osteoporosis. Urinary incontinence during coughing episodes is common and can be embarrassing and limiting.

Other complications in this age group include hernias (from increased abdominal pressure during coughing), fainting during or after coughing fits (cough syncope), pulled muscles, and subconjunctival hemorrhages (bleeding in the whites of the eyes). Weight loss from post-tussive vomiting and the physical demands of coughing is also common during prolonged illness.

How Is Whooping Cough Diagnosed?

Whooping cough is diagnosed through clinical assessment of symptoms and confirmed with laboratory testing. The most accurate test is PCR (polymerase chain reaction) from a nasopharyngeal swab, which detects bacterial DNA. Culture is the gold standard but less sensitive. Blood tests for antibodies can help diagnose later-stage disease when other tests may be negative.

Diagnosing whooping cough requires a combination of clinical assessment and laboratory confirmation. Early diagnosis is crucial because antibiotic treatment is most effective when started early in the illness, and prompt identification allows for prophylactic treatment of close contacts before they become ill.

Clinical Diagnosis

Healthcare providers consider whooping cough when a patient presents with a cough lasting more than 2 weeks, particularly when accompanied by paroxysms (sudden fits), post-tussive vomiting, or the characteristic whooping sound. The clinical case definition used by public health authorities typically requires a cough lasting at least 2 weeks with at least one of these characteristic features.

However, clinical diagnosis alone is challenging because vaccinated individuals, infants, and adults often present with atypical symptoms. The classic "whoop" may be absent, and the cough may be the only prominent symptom. This is why laboratory confirmation is important, especially during outbreaks or when the diagnosis will affect treatment of close contacts.

Laboratory Testing

PCR Testing: Polymerase chain reaction (PCR) testing is currently the most widely used and sensitive method for confirming whooping cough. A healthcare provider collects a sample from the back of the nose (nasopharyngeal swab) or the throat. PCR can detect Bordetella pertussis DNA even when the bacteria are no longer viable, making it useful for several weeks after symptom onset. However, sensitivity decreases significantly after 3-4 weeks of illness.

Bacterial Culture: Growing the bacteria in the laboratory from a nasopharyngeal specimen is the "gold standard" for diagnosis and is 100% specific. However, culture is less sensitive than PCR (30-60% sensitivity), takes 3-7 days for results, and becomes negative within 2 weeks of illness onset or after antibiotic treatment begins. It is most useful in the early stages of disease.

Serology (Blood Tests): Blood tests that measure antibodies against pertussis toxin can be helpful for diagnosing whooping cough in later stages of illness when PCR and culture may be negative. This test is particularly useful in adolescents and adults who often present later in the disease course. However, interpretation can be complicated by recent vaccination, and not all laboratories offer this testing.

How Is Whooping Cough Treated?

Whooping cough is treated with macrolide antibiotics—azithromycin (5 days) is the first-line treatment, with alternatives including clarithromycin (7 days) or erythromycin (14 days). Antibiotics are most effective when started within 3 weeks of cough onset. Treatment reduces transmission (no longer contagious after 5 days) but may not shorten the cough duration if started late. Supportive care is essential.

The treatment of whooping cough combines antibiotic therapy to eliminate the bacteria with supportive care to manage symptoms and prevent complications. The goals of treatment are to reduce disease severity, shorten the duration of illness when possible, and prevent transmission to others, particularly vulnerable contacts like infants.

Antibiotic Treatment

Macrolide antibiotics are the primary treatment for whooping cough. The choice of antibiotic depends on the patient's age, other medications, and any allergies:

• Azithromycin: The preferred antibiotic for most patients. Adults and children over 6 months receive a 5-day course. For infants 1-5 months, the dose is 10 mg/kg once daily for 5 days. Azithromycin is preferred in infants under 1 month because other macrolides are associated with pyloric stenosis in this age group.
• Clarithromycin: An alternative 7-day course for patients who cannot tolerate azithromycin. Not recommended for infants under 1 month.
• Erythromycin: The traditional treatment, given for 14 days. Still effective but has more gastrointestinal side effects and requires more frequent dosing.
• Trimethoprim-sulfamethoxazole (TMP-SMX): Alternative for patients allergic to macrolides. Not used in infants under 2 months or pregnant women.

The timing of antibiotic treatment significantly affects outcomes. When started within the first 3 weeks of illness (ideally during the catarrhal stage or early paroxysmal stage), antibiotics can reduce the severity and duration of symptoms. If started later, antibiotics may not shorten the illness but still provide important benefits by eliminating bacteria and stopping transmission to others.

Supportive Care

Because antibiotics have limited effect on symptoms once coughing paroxysms are established, supportive care is a critical component of treatment:

• Rest: Patients should rest as much as possible, as fatigue can trigger and worsen coughing fits
• Hydration: Adequate fluid intake is essential, especially given the risk of dehydration from vomiting. Small, frequent sips are better tolerated than large amounts
• Nutrition: Small, frequent meals are easier to keep down. Eating after coughing episodes rather than before may reduce vomiting
• Avoiding triggers: Smoke, dust, chemical fumes, cold air, and strong scents can trigger coughing paroxysms
• Humidified air: Some patients find relief with cool-mist humidifiers, though evidence for effectiveness is limited

Hospital Treatment for Severe Cases

Hospitalization is often necessary for infants with whooping cough and for patients of any age with severe disease. In the hospital, treatment may include oxygen supplementation, intravenous fluids, suctioning of secretions, and close monitoring for apnea and respiratory failure. In the most severe cases, mechanical ventilation may be required.

How Can Whooping Cough Be Prevented?

Vaccination is the most effective way to prevent whooping cough. The DTaP vaccine is given to children in a 5-dose series starting at 2 months of age. A Tdap booster is recommended at age 11-12, during every pregnancy (ideally at 27-36 weeks), and for adults who have never received it. Close contacts of infected individuals should receive preventive antibiotics.

Prevention of whooping cough relies on three main strategies: vaccination to prevent disease, post-exposure prophylaxis with antibiotics for close contacts, and infection control measures to limit transmission. Of these, vaccination is by far the most effective approach and has dramatically reduced the burden of disease worldwide.

Vaccination: The Best Protection

Pertussis vaccines have been available since the 1940s and are responsible for a greater than 80% reduction in whooping cough cases and deaths. Current vaccines are acellular vaccines (aP), which contain purified components of the Bordetella pertussis bacterium rather than whole killed bacteria. These vaccines are given in combination with tetanus and diphtheria vaccines.

DTaP (Diphtheria, Tetanus, Pertussis) for Children: The primary vaccination series consists of 5 doses given at 2 months, 4 months, 6 months, 15-18 months, and 4-6 years of age. This series provides excellent protection during early childhood when the risk of severe disease is highest. After the primary series, immunity gradually wanes over 4-12 years.

Tdap (Tetanus, Diphtheria, Pertussis) Booster: A booster dose is recommended at age 11-12 to address waning immunity. Adults who have never received a Tdap vaccine should receive one dose, regardless of when their last Td (tetanus-diphtheria) booster was given. Subsequent boosters can be either Td or Tdap every 10 years.

Vaccination During Pregnancy: Vaccination with Tdap during each pregnancy, ideally between 27 and 36 weeks of gestation, is one of the most important strategies for protecting newborns. The mother's immune response produces antibodies that cross the placenta and provide the infant with passive protection during the first months of life before the infant's own vaccinations take effect. This strategy has been shown to prevent more than 90% of whooping cough cases in infants under 2 months of age.

Post-Exposure Prophylaxis

Close contacts of individuals with confirmed or suspected whooping cough should receive preventive antibiotic treatment, regardless of vaccination status. This is particularly important for household members and anyone who will have close contact with infants or other high-risk individuals. The same antibiotics used for treatment (azithromycin, clarithromycin, or erythromycin) are used for prophylaxis, and treatment should begin within 21 days of exposure to be effective.

Infection Control Measures

Patients with whooping cough should be isolated from susceptible individuals, particularly infants, until they have completed 5 days of appropriate antibiotic treatment or, if untreated, for 21 days after the onset of cough. Additional measures include frequent handwashing, covering coughs with tissues or the elbow, and proper disposal of used tissues.

When Should You Seek Medical Care?

Seek medical care if you or your child has a persistent cough lasting more than 2 weeks, especially with coughing fits, vomiting after coughing, or a whooping sound. Seek emergency care immediately for breathing difficulties, apnea (breathing pauses), turning blue or pale, inability to keep down fluids, or any concerning symptoms in infants under 6 months.

Recognizing when to seek medical care for whooping cough is crucial for ensuring appropriate treatment and preventing complications. The urgency of care depends on age, symptom severity, and underlying health conditions.

Contact a Healthcare Provider If:

• You or your child has a cough lasting more than 2 weeks
• The cough comes in intense fits followed by gasping
• Vomiting occurs after coughing episodes
• A whooping sound is heard when breathing in after coughing
• The face turns red during coughing fits
• You've had contact with someone diagnosed with whooping cough
• Your child has not completed their vaccination series

Living With Whooping Cough: Recovery and Outlook

Recovery from whooping cough takes 6-10 weeks on average, though the cough may persist for months. Most children and adults recover completely without lasting effects. The cough gradually becomes less severe and less frequent during the convalescent stage. The risk of re-infection exists as immunity wanes over time, though subsequent infections are usually milder.

The recovery period for whooping cough is often longer than patients and families expect. Understanding the normal course of recovery can help set realistic expectations and identify when improvement is occurring, even when the cough persists.

What to Expect During Recovery

During the convalescent stage, coughing paroxysms gradually become less frequent and less severe. The time between episodes lengthens, and the force of the cough diminishes. However, it's common for the cough to persist for several months, and any respiratory infection during this time may trigger a return of whooping cough-like symptoms.

Physical recovery may be complete, but the psychological impact of prolonged severe coughing should not be underestimated. Many patients experience anxiety related to coughing episodes, sleep disturbances, and fatigue that persists beyond the active infection. Patience and gradual return to normal activities are important.

When to Resume Normal Activities

Patients should avoid contact with infants and unvaccinated individuals until they are no longer contagious—either after completing 5 days of antibiotics or 21 days after cough onset if untreated. Return to school or work can generally occur after this period, though fatigue may require a gradual return to full activities.

Long-Term Outlook

The prognosis for whooping cough is generally excellent, particularly for vaccinated individuals and those who receive early treatment. Most people recover completely without lasting effects. However, infants who experience complications such as pneumonia, seizures, or encephalopathy may have long-term neurological or respiratory consequences.

Neither natural infection nor vaccination provides lifelong immunity. Protection wanes over 4-12 years, making re-infection possible. However, subsequent infections in previously infected or vaccinated individuals tend to be milder than first-time infections, demonstrating that partial immunity persists even as complete protection fades.