Pertussis, or whooping cough, is an acute respiratory tract infection that continues to affect a significant portion of the global population, with more than 24 million estimated cases in 2014.¹ Pertussis, a Centers for Disease Control and Prevention (CDC) reportable disease, is caused by Bordetella pertussis. The disease can lead to substantial complications in infants, such as apnea, pneumonia, seizures, other hypoxic complications, hospitalization, or death.^2,3 Bordetella parapertussis and rarely Bordetella bronchiseptica can also cause a pertussis-like syndrome.

The incidence of pertussis in the United States decreased with universal childhood immunization, but it has rebounded steadily in recent years, from a low of 1,010 reported cases in 1976 to a peak of 48,277 cases in 2012.⁴ The most recent available data show 15,609 reported cases in 2018.⁵

What Is the Typical Presentation and Progression of Pertussis?

There are three stages of pertussis (catarrhal, paroxysmal, and convalescent), each with a different clinical presentation (Table 1).^6–8 However, clinical presentation varies widely depending on age and immunization status, and not every patient has the classic stage progression.⁹

EVIDENCE SUMMARY

The key clinical features of the initial catarrhal stage are difficult to distinguish from a viral upper respiratory tract infection and include malaise, rhinorrhea, dry cough, and lacrimation. Fever is usually mild or absent. After one to two weeks, the paroxysmal stage may manifest. Typical features of this stage include paroxysmal coughing, whooping on inspiration after coughing, and posttussive emesis.

Other common features of the paroxysmal stage include periods of apnea associated with paroxysms, chest and abdominal soreness from prolonged coughing, and scleral hemorrhage. In between paroxysms, the patient may be asymptomatic. The paroxysmal stage typically lasts up to six weeks before transitioning to the convalescent stage. In this stage, the coughing lessens but typically persists for an additional two to four weeks, with some patients experiencing symptoms for a longer period (e.g., “100-day cough”).^7,10–12

Can Pertussis Be Diagnosed with Clinical Signs and Symptoms Alone, or Is Laboratory Testing Required?

The diagnosis of pertussis requires laboratory confirmation. Because early detection and treatment are critical to reducing transmission, accurate identification of the clinical features of pertussis is important to prompt testing.

EVIDENCE SUMMARY

No validated, accepted clinical decision rule has been established for diagnosing pertussis.¹³ However, the key clinical features of the infection are included in CDC and World Health Organization (WHO) case definitions. The CDC case definition of pertussis includes coughing of any duration and at least one sign or symptom (i.e., paroxysmal coughing, inspiratory whooping, posttussive emesis, or apnea) and contact with a laboratory-confirmed case of pertussis, or at least two weeks of coughing and one of these signs or symptoms.¹⁴ The WHO definition adds the clinical suspicion of pertussis and specifies that apnea is a criterion only in infants younger than one year.¹⁵ Although sensitive, the CDC and WHO criteria lack specificity.¹³

Two 2017 systematic reviews evaluated the clinical features used in the diagnosis of pertussis (Table 2).^13,16 One found that the best clinical predictors of pertussis in adults were the presence of whooping (positive likelihood ratio [LR+] = 1.45) and posttussive emesis (LR+ = 1.46), and the best negative predictors were a lack of paroxysmal coughing (negative likelihood ratio [LR−] = 0.33) and presence of fever (LR− = 0.97).¹⁶ However, the second systematic review reported minimal value of individual signs and symptoms, with the clinician's overall impression having the highest likelihood ratio out of both reviews (LR+ = 3.3).¹³