Adult-to-child transmission of tuberculosis: household or community contact?
METHODS
If a child develops tuberculosis, it is assumed that the source was an adult infectious case, usually living in the same house. Restriction fragment length polymorphism (RFLP) was used in this study to establish transmission from source cases to children.


METHODS
Adult and child tuberculosis cases were prospectively identified from 1993 to 1998 and cultures of Mycobacterium tuberculosis collected. Interviews and RFLP analysis of M. tuberculosis strains were performed to establish epidemiological links and to confirm household transmission.


RESULTS
Tuberculosis was confirmed by culture in 1139 (91%) of 1291 adults and 65 (16%) of 417 children. Due to problems in recovering specimens or extracting DNA, RFLP analysis was done in 832 adults and 35 children: 19 (54%) children had household members identified with tuberculosis, 12 with the same strain as the child. Twenty-nine (83%) strains from children formed part of community clusters, but definite contact with source cases was established in only 15.


CONCLUSIONS
The presence of an adult with infectious tuberculosis in the same house as a child with tuberculosis does not necessarily imply adult-to-child transmission. Young children may be infected in the community or in the household. These findings have implications for contact tracing and treatment strategies in high incidence areas.
Schaaf
H S
HS
Department of Paediatrics and Child Health, Faculty of Health Sciences, Stellenbosch University, Tygerberg, South Africa. hss@sun.ac.za
Michaelis
I A
IA
Richardson
M
M
Booysen
C N
CN
Gie
R P
RP
Warren
R
R
van Helden
P D
PD
Beyers
N
N
D000328:Adult; D002648:Child; D017714:Community-Acquired Infections; D005192:Family Health; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D012150:Polymorphism, Restriction Fragment Length; D011446:Prospective Studies; D013019:South Africa / Q000453:epidemiology; D014376:Tuberculosis / Q000453:epidemiology / Q000235:genetics / Q000635:transmission*