Babies under 12 months of age often require admission to hospital. Complications include convulsions, pneumonia, coma, inflammation of the brain, and permanent brain damage. Around one in every 200 children under six months of age who contracts pertussis will die. The most common cause of death is from pertussis pneumonia. Pertussis is a highly infectious disease, typically transferred to 70-100 per cent of susceptible household contacts.
Infection is spread by direct contact with droplets from the nose and throat of an infected person.
The incubation period is commonly 7-10 days and not more that 21 days. A case is infectious from 7 days after exposure to 3 weeks after the onset of typical paroxysms. Children should be excluded from child care until well and until five days after starting antibiotic treatment. During epidemics cases occur mainly in school aged children, who then pass it on to younger siblings. Adolescents and adults may also be reservoirs of infection.