The bacteria secretes a number of toxins. Tracheal cytotoxin, a fragment of peptidoglycan, kills ciliated epithelial cells and thereby inhibits the mucociliary elevator by which mucus and debris are removed. TCT may contribute to the cough characteristic of pertussis. The cough may also be caused by a yet-to-be identified “cough toxin”. Pertussis toxin causes lymphocytosis by an unknown mechanism. The elevated number of white blood cells leads to pulmonary hypertension, a major cause of death by pertussis.
A physician’s overall impression is most effective in initially making the diagnosis. Single factors are much less useful. In adults with a cough of less than 8 weeks, vomiting after coughing or a “whoop” is supportive. If there are no bouts of coughing or there is a fever the diagnosis is unlikely. In children who have a cough of less than 4 weeks vomiting after coughing is somewhat supportive but not definitive.
The multicomponent acellular pertussis vaccine is 71–85% effective, with greater effectiveness against more severe strains. However, despite widespread vaccination, pertussis has persisted in vaccinated populations and is today “one of the most common vaccine-preventable diseases in Western countries”.The 21st-century resurgences in pertussis infections is attributed to a combination of waning immunity and bacterial mutations that elude vaccines
Some studies have suggested that while acellular pertussis vaccines are effective at preventing the disease, they have a limited impact on infection and transmission, meaning that vaccinated people could spread pertussis even though they may have only mild symptoms or none at all. Pertussis infection in these persons may be asymptomatic, or present as illness ranging from a mild cough to classic pertussis with persistent cough . Even though the disease may be milder in older persons, those who are infected may transmit the disease to other susceptible persons,