Pertussis: Recognizing and Treating a Resurging Respiratory Infection

Lilian White, MD
Posted on July 21, 2025

Approximately 10,000 cases of pertussis are reported annually by the Centers for Disease Control and Prevention. As with other bacterial and viral respiratory infections, reported cases of pertussis waned during the pandemic and are now increasing again postpandemic. Infants (younger than 1 year) have the highest morbidity and mortality from pertussis. Of infants who were hospitalized or died from pertussis, the majority (54% and 85%, respectively) were younger than 2 months of age.

An AFP Common Questions and Answers article notes that pertussis often—though not always—presents in three stages: catarrhal, paroxysmal, and convalescent. The catarrhal (or inflammatory) stage includes the insidious onset of upper respiratory symptoms without fever for approximately 1 to 2 weeks. Patients are highly contagious during this stage, but symptoms are often nonspecific, making prevention of infectious spread to others difficult. The paroxysmal stage often includes the trademark whooping cough along with posttussive emesis. In the convalescent stage, symptoms gradually improve over 2 to 4 weeks.

Diagnosis of pertussis is often clinical. The sign with the highest positive likelihood ratio (LR+) is the physician’s overall clinical impression, with LR+ = 3.3. Inspiratory whooping has the highest LR+ in children (LR+ = 2.9). This is closely followed by posttussive emesis, with a LR+ = 1.7 for both adults and children. Symptoms that make pertussis less likely include the absence of paroxysmal (sudden and/or intense fits of) coughing in adults and absence of posttussive emesis in children, with negative likelihood ratios of 0.33 and 0.61, respectively.

Polymerase chain reaction (PCR) testing is considered the most accurate and preferred confirmatory test within the first 4 weeks of illness. PCR testing results may not be timely depending on the lab, limiting its clinical usefulness. However, similar to other infectious diseases, some companies offer rapid PCR testing with results available within 24 hours. If PCR testing is not available, culture may be considered. Serology may be preferred later in the disease course (more than 3 weeks); however, serology may not be accurate in those who have been vaccinated within the last 12 months or are younger than 6 months. Leukocytosis with a lymphocytic predominance in infants younger than 3 months is supportive of a diagnosis of pertussis.

Treatment of pertussis is largely supportive. Antibiotics may reduce disease transmission if given within 21 days of symptom onset but do not appear to improve symptoms or time to recovery. Macrolide antibiotics (especially azithromycin) and trimethoprim-sulfamethoxazole are typically recommended. Postexposure prophylaxis within 21 days of exposure is recommended for household contacts and high-risk close contacts of patients with pertussis. Administering vaccines is not recommended for postexposure prophylaxis.

Recommendations for the DTaP and TDaP vaccines for prevention of pertussis may be found on the CDC website.