Epidemiology Prior to vaccine availability, the estimated incidence of pertussis was 100 cases per 100,000 population.3 From 1922 to 1948, pertussis ranked as the leading cause of death from communicable disease among children in the U.S. less than 14 years old.1 After the vaccine was introduced, cases dropped to 0.5 to 1.5 cases per 100,000. Complications from pertussis also occur most frequently in children during their first year of life. However, older persons with underlying disease such as asthma or cystic fibrosis can become very ill. Following exposure to B. pertussis, the incubation period ranges from 7 to 21 days. The organism produces several virulence factors that are responsible for the pathogenesis and clinical features of the disease.
Pertussis is primarily a toxin-mediated disease.
This damage results in improper functioning and inflammation of the respiratory epithelial cells.1,7 Pertussis antigens appear to allow the organism to evade host defenses, in that lymphocytosis is promoted but chemotaxis is impaired. Patients are most contagious during the catarrhal stage which typically lasts 1 to 2 weeks. The paroxysmal stage is marked by worsening of the cough which evolves into paroxysms, or short expiratory bursts, followed by an inspiratory gasp which can result in the classic whoop. Infants, older children and adults may have the cough with no whoop. The attacks may be severe enough to cause cyanosis and often end with an episode of vomiting.