Bordetella pertussis PCR positivity, following onset of illness in children under 5 years of age.

Bordetella pertussis is a significant cause of respiratory illness and an ongoing public health problem. Pertussis polymerase chain reaction (PCR) testing has been widely utilised since 2001, especially in infants. Uncertainty exists as to how long PCR remains positive following symptom onset. Further information on the time frame for pertussis PCR testing would assist diagnosis, epidemiological research and disease control. The Brisbane Southside Population Health Unit (BSPHU) conducted a retrospective analysis of enhanced surveillance data from pertussis notifications between January 2001 and December 2005, in children less than 5 years of age, in the BSPHU reporting area with the aim to determine the possible range of duration of Bordetella pertussis PCR, from symptom onset for this age group. Of 1,826 pertussis notifications to BSPHU between January 2001 and December 2005, 155 (8.5%) were children under 5 years of age, with 115 pertussis PCR positive results. Analysis indicated a range of PCR positivity from day one to day 31 from the onset of catarrhal symptoms with most (84%) being within 21 days from onset of catarrhal symptoms. The range of PCR positivity following onset of paroxysmal cough was from day one to day 38 with most (89%) being within 14 days from the onset of paroxysmal cough. This review of pertussis PCR data in young children showed that PCR positive results generally mirrored the understood length of infectivity with regard to both catarrhal symptoms and paroxysmal cough; namely that PCR positive results were obtained at least 21 days following onset of catarrhal symptoms and at least 14 days following onset of paroxysmal cough.