A network-informed approach to investigating a tuberculosis outbreak: implications for enhancing contact investigations.
BACKGROUND
To elucidate networks of Mycobacterium tuberculosis transmission, it may be appropriate to characterize the types of relationships among tuberculosis (TB) cases and their contacts (with and without latent TB infection) in addition to relying on traditional efforts to distinguish 'close' from 'casual' contacts.


METHODS
A TB outbreak in a US low incidence state.


OBJECTIVE
To evaluate whether social network analysis can provide insights into transmission settings that might otherwise go unrecognized by routine practices.


METHODS
All adult outbreak-associated cases (n = 19) and a convenience sample of their contacts with and without latent TB infection (LTBI) (n = 26) were re-interviewed in 2001 using a structured questionnaire. Network analysis software was used to create diagrams illustrating important persons within the outbreak network, as well as types of activities TB cases engaged in with their contacts.


RESULTS
Drug use and drug sharing were more commonly reported among cases and their infected contacts than among contacts without LTBI. TB cases central to the outbreak network used crack cocaine, uncovering the need to focus control efforts on specific sites and persons involved in illicit drug use.


CONCLUSIONS
Outbreaks occur even in areas with low TB incidence, frequently among groups whose drug use or other illegal activities complicate control efforts. TB programs should consider the use of network analysis as a supplement to routine contact investigations to identify unrecognized patterns of M. tuberculosis transmission.
McElroy
P D
PD
Surveillance and Epidemiology Branch, Division of Tuberculosis Elimination, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. pgm9@cdc.gov
Rothenberg
R B
RB
Varghese
R
R
Woodruff
R
R
Minns
G O
GO
Muth
S Q
SQ
Lambert
L A
LA
Ridzon
R
R
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D019058:Community Networks; D016358:Contact Tracing / Q000379:methods*; D004196:Disease Outbreaks; D005260:Female; D006801:Humans; D007223:Infant; D007615:Kansas / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012725:Sexual Behavior; D012919:Social Behavior; D019966:Substance-Related Disorders / Q000150:complications; D014376:Tuberculosis / Q000175:diagnosis / Q000453:epidemiology* / Q000635:transmission*