Pertussis (or whooping cough) is a frequent and important infectious disease of the respiratory tract, mainly caused by the Gram-negative rod bacterium Bordetella pertussis. Although it is frequently believed that pertussis is exclusively a 'childhood disease', in reality it occurs at any age but is most serious in young infants. Adults are the main reservoir for B. pertussis today and pertussis remains an endemic disease worldwide despite the availability of comprehensive immunization programs that primarily target the pediatric population. There are many reasons for these, and these include incomplete immunity following natural infection as well as immunization and waning immunity over time. Manifestations of B. pertussis infections vary by magnitude of the bacterial inoculum, age, immune status and probably further yet unidentified individual factors. They can range from asymptomatic, apnea and uncharacteristic cough to typical coughing spells with posttussive phlegm and/or vomiting, and duration also varies between a few days and several months. Since antibacterial treatment of pertussis is generally ineffective as it usually sets in too late, the main focus should be on the prevention of pertussis by immunization. This apparently requires more than immunization of children--that is, expanding routine immunization into adolescence and adulthood.