Incidence and Diagnosis of Pertussis in South African Children Hospitalized with Lower Respiratory Tract Infection.

The incidence of pertussis in children in low and middle-income countries is poorly described. This study aimed to prospectively investigate the incidence of pertussis in South African children hospitalized with lower respiratory tract infection (LRTI).
Children hospitalized with LRTI in Cape Town, South Africa were enrolled over one year. Clinical data were collected. A nasopharyngeal swab (NP) and induced sputum (IS) were taken and PCR specific for Bordetella pertussis (IS481+/hIS1001-) and Bordetella parapertussis (IS1001+) was performed.
460 children with median age 8 (IQR 4-18) months were studied. Bordetella pertussis was detected in 17 (3.7%) while total Bordetella spp. were identified on 23 (5.0 %) of 460 NP. Adding IS testing increased the identification of B. pertussis to 32/460 cases (7.0%; 95% CI 4.8-9.7%); p=0.028 and total Bordetella to 41/460 (8.9%; 95% CI 4-10%); p=0.020. Shorter duration of symptoms [median 2 (IQR 2-3) days versus 5 (IQR 3-7) days; p=0.0008] was associated with detection of B. pertussis on IS versus NP.B. pertussis was detected in 15.8% (n=3/19) of HIV infected children, 10.9% (n=10/92) of HIV exposed uninfected and 5.4% (n=19/349) of HIV unexposed uninfected children. Risk of B. pertussis decreased with each additional dose of DTaP vaccine [0 doses = 17.9%; 1 dose =7.0%; 2 doses =6.9%; >3 doses =6.2%].
Pertussis is common in South African children hospitalized with LRTI particularly if HIV exposed or infected but decreases sequentially with vaccination doses. PCR on IS specimen provides confirmation earlier than NP while increasing overall diagnostic yield.

Authors:Muloiwa R1, Dube FS, Nicol MP, Zar HJ, Hussey GD.
Journal:Pediatr Infect Dis J. 2016