To evaluate the usefulness of real-time polymerase chain reaction (RT-PCR) as a diagnostic method for the detection of Bordetella pertussis in hospitalized patients aged <1 year with a clinical diagnosis of whooping cough, as well as to identify the role of household contacts as a source of infection.

This was a prospective, multicenter study of infants aged <1 year who were hospitalized with symptoms suggestive of whooping cough. Nasopharyngeal samples were obtained for culture and RT-PCR testing. The clinical and epidemiologic characteristics and outcomes were analyzed. B pertussis detection and symptoms in household contacts of patients diagnosed with pertussis were studied.

A total of 286 patients were included; of these, 67.1% had B pertussis and 4.5% had Bordetella spp. Complications occurred in 20% of patients, and the mortality rate was 6.7%. Of 434 contacts studied, 111 were mothers of study infants, representing the most frequently B pertussis–infected group and the main symptomatic contact.

The use of RT-PCR permits improved detection and diagnosis of pertussis and a better understanding of the epidemiology of sources of infection. The complications and mortality rate of pertussis continue to be high. Household contacts are confirmed as a frequent source of infection of B pertussis in young children.