Last updated on: February 10th, 2021

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Clinicals - History

Known exposure to pertussis

Pertussis, or whooping cough, is caused by the bacteria Bordetella pertussis. It is easily transmitted from person to person via airborne droplets. Contact with a known case of pertussis should raise suspicion for the disease in any symptomatic patient.

Stage 1: Catarrhal

Generally occurs 5 to 10 days after exposure and lasts 7 to 10 days. At this time there is coryza, low-grade fever, and a mild cough that gradually worsens.

Stage 2: Paroxysmal

This phase generally lasts 1 to 6 weeks. The classic triad of symptoms is paroxysms of cough, whooping on inspiration, and post-tussive vomiting. The paroxysms may be worse in older infants and young children, and are generally milder in adolescents and adults, especially if immunized. They are often absent in young infants.

This occurs due to the inability to expel mucus from tracheobronchial tree.

Stage 3: Convalescent

This phase lasts 2 to 6 weeks or longer. There is a gradual resolution of the paroxysmal cough. However, paroxysms may return with respiratory infections for several months.

Prolonged cough without paroxysms

The classic triad may be absent, especially in adolescents, adults, and immunized children.


Infants may be without the classic symptoms and exhibit only apnea.

Neurologic complications

Seizures and encephalopathy may occur in infants. Encephalopathy is thought to be either due to lack of oxygenation or a direct effect of bacterial toxins.

Clinicals - Examination


Usually low-grade; may be absent, especially outside of catarrhal stage.

Respiratory distress

In distress during coughing paroxysms. Cyanosis may be present. Generally without respiratory distress when not coughing.

Signs of pneumonia

Bacterial pneumonia is sometimes a complication. If pneumonia is present, there may be fever, dyspnea, tachypnea, decreased breath sounds, and crackles. Otherwise the lung examination is likely to be normal.

Differential Diagnoses

Upper respiratory infection

In early stages, it may be difficult to differentiate pertussis from an upper respiratory infection. The later development of paroxysmal cough and its associated symptoms (whoop, vomiting after cough) increases suspicion for pertussis.


Although bacterial pneumonia may be a complication of pertussis, classic pertussis without this complication is unlikely to have fever, dyspnea, tachypnea or an abnormal lung examination.


Wheezing and decreased air movement is usually present in symptomatic asthma. These findings can occur in pertussis but are less common.


Usually influenza has a high fever, which is less likely in pertussis.

Acute bronchitis

This is often associated with wheezes and rhonchi, which are less likely in pertussis.

Tracheoesophageal foreign body

Wheezing and decreased air movement is likely to accompany the paroxysmal cough when a foreign body is present. Definitive diagnosis is by flexible fiberoptic bronchoscopy.

Other viral respiratory illnesses

Respiratory syncytial virus may have dyspnea and wheezing associated. Some evidence exists for potential co-infection with pertussis.

Investigations - Diagnosis

Clinical impression

When classic symptoms are present, the clinical impression is relatively predictive of actual bordetella pertussis infection.

Pertussis polymerase chain reaction assay

Obtained via nasopharyngeal (NP) swab. Most accurate within the first 3 weeks. Fastest turnaround time of all diagnostic tests, but may still take several days to come back.

Pertussis culture

Should be obtained within the first 2 weeks of illness. Specific but not very sensitive. Sensitivity further wanes after 2 weeks.

Paired serology

Use at this time is controversial. No longer recommended by the Centers for Disease Control (CDC).

Investigations - Management

Complete blood count

Pertussis generally shows a marked lymphocytosis (leukopenia may be seen early on).

Higher white blood cell counts are associated with poorer outcomes; it is thought that they contribute to pulmonary hypertension by blocking pulmonary capillaries and restricting blood flow.

Management - Supportive


May be warranted especially in young children, due to increased complications. Death occurs in approximately 1 percent of infants.

Avoid certain medications

No benefit has been found with antitussives, antihistamines, steroids, beta agoists, or immunoglobulins. Antitussives are contraindicated in infants and young children.

Exchange transfusion

Exchange transfusion has been used in some critically ill infants to reduce leukocytosis.

Management - Specific


Macrolides are drugs of choice. In most cases azithromycin is first choice due to the short course and good tolerability. In infants, macrolides have some association with idiopathic hypertrophic pyloric stenosis, but azithromycin is less associated with this.

There are recent reports of azithromycin being associated with arrhythmias; consider alternatives for patients with heart disease. Other possibilities: clarithromycin, erythromycin. Use trimethoprim-sulfamethoxazole in macrolide-allergic patients.

Antibiotics may lessen symptoms if started within 1 to 2 weeks; otherwise treatment is mainly to prevent transmission. Importantly, treatment can be commenced on clinical suspicion, and should not be delayed pending investigation results.

Treat exposed contacts

Treat close contacts within three weeks of exposure. The same antibiotics and doses are used.

Prevention: Immunization

Pertussis vaccine is recommended beginning at age 2 months; generally children receive 5 doses through kindergarten entry. A dose of Tdap vaccine is also given around middle school entry, age 11 or 12.

Post-exposure prophylaxis

As there is no guarantee of life long immunity post-infection, the pertussis vaccine should be administered as per standard recommendations, for post-exposure prophylaxis.

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