Whooping cough is predominantly a disease of childhood.
Whooping cough is endemic worldwide and affects more than 600,000 million people annually. This is an important cause of mortality in children with estimated 51,000,000 cases and 600,000 deaths annually, particularly in the countries where vaccines are not used regularly.
B. pertussis colonizes the cilia of mammalian respiratory epithe-lium of infected children.
Whooping cough is highly contagious. Humans are the only known reservoir of B. pertussis infection. An infected child, par-ticularly during catarrhal stage of disease, is the important source of infection. The infection is transmitted primarily by inhalation of air-borne droplets coughed out by the infected patients. The infection is also transmitted by contact with hard surfaces recently contaminated with respiratory secre-tions or droplets from an infected child. Secondary attack rates are highest (75–100%) among unimmunized household contacts.
Initially, whooping cough was considered to be a disease of young children (,5 years), but now this disease is also seen in older children and adults. They contribute to 25% of cases of whooping cough. This is due to failing immunity over time in adults, even in those who are vaccinated.