Whooping Cough

Abstract

First described in the sixteenth century, whooping cough or pertussis is a relatively recent disease in human history, although some of the cough syndromes described in antiquity may in fact be pertussis-like diseases. Whooping cough caused by the gram-negative bacterium Bordetella pertussis is a severe respiratory disease, especially life-threatening in early childhood. In addition to respiratory symptoms, characterized by paroxysmal cough and whoop, pertussis also manifests itself by a marked leukocytosis, and complications due to superinfections are common. In adolescents, adults, and vaccinated older children, the disease is often atypical. It was a major cause of childhood mortality in the pre-vaccination era. Mass vaccination has tremendously reduced the incidence of the disease, but despite a large global vaccination coverage, we witness a dramatic increase of its incidence in recent years. The pathogenesis of the disease relies on a series of rather well-defined virulence factors, including several adhesins and toxins, whose production is controlled at the transcriptional level by a two-component master regulatory system. Various animal models have helped to decipher the virulence mechanisms of B. pertussis and have been instrumental in preclinical testing of vaccines. However, most of them do not reflect all the features of human pertussis, perhaps with the exception of a very recent baboon model. Since the discovery of its etiological agent, different diagnostic methods have been designed, including bacterial culture, serology, and, more recently, polymerase chain reaction. B. pertussis is sensitive to several antibiotics. Erythromycin is the drug of choice, and erythromycin-resistant B. pertussis isolates are rare. However, unless administered at the early catarrhal stage of the disease, antibiotic treatment is of little help to decrease the severity or to shorten the duration of the disease. Vaccination is today the most powerful tool to combat the disease. Several types of vaccines are currently available, including the whole-cell first-generation vaccines and the newer acellular second-generation vaccines. However, in view of the recent reemergence of pertussis, current vaccine regimens have shown their limits, and new vaccines are urgently needed. In that regard, live attenuated vaccines given very early in life may perhaps be able to protect the youngest and most vulnerable infants during the first months of life.