The transmission dynamics of tuberculosis in a recently developed Chinese city.
BACKGROUND
Hong Kong is an affluent subtropical city with a well-developed healthcare infrastructure but an intermediate TB burden. Declines in notification rates through the 1960s and 1970s have slowed since the 1980s to the current level of around 82 cases per 100 000 population. We studied the transmission dynamics of TB in Hong Kong to explore the factors underlying recent trends in incidence.


RESULTS
We fitted an age-structured compartmental model to TB notifications in Hong Kong between 1968 and 2008. We used the model to quantify the proportion of annual cases due to recent transmission versus endogenous reactivation of latent infection, and to project trends in incidence rates to 2018. The proportion of annual TB notifications attributed to endogenous reactivation increased from 46% to 70% between 1968 and 2008. Age-standardized notification rates were projected to decline to approximately 56 per 100 000 in 2018.


CONCLUSIONS
Continued intermediate incidence of TB in Hong Kong is driven primarily by endogenous reactivation of latent infections. Public health interventions which focus on reducing transmission may not lead to substantial reductions in disease burden associated with endogenous reactivation of latent infections in the short- to medium-term. While reductions in transmission with socio-economic development and public health interventions will lead to declines in TB incidence in these regions, a high prevalence of latent infections may hinder substantial declines in burden in the longer term. These findings may therefore have important implications for the burden of TB in developing regions with higher levels of transmission currently.
Wu
Peng
P
Department of Community Medicine and School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
Lau
Eric H Y
EH
Cowling
Benjamin J
BJ
Leung
Chi-Chiu
CC
Tam
Cheuk-Ming
CM
Leung
Gabriel M
GM
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D002648:Child; D002675:Child, Preschool; D002947:Cities / Q000453:epidemiology*; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008954:Models, Biological; D015999:Multivariate Analysis; D014376:Tuberculosis / Q000453:epidemiology* / Q000635:transmission*; D055815:Young Adult
J R Soc Interface. 2007 Jun 22;4(14):523-31
17251134
Am J Epidemiol. 1974 Feb;99(2):131-8
4810628
N Engl J Med. 1999 Oct 14;341(16):1226-7
10519901
Int J Epidemiol. 2004 Dec;33(6):1219-26
15567872
J Clin Microbiol. 2003 Jun;41(6):2706-8
12791911
Thorax. 2008 Apr;63(4):312-6
18024541
Int J Tuberc Lung Dis. 2004 Mar;8(3):278-85
15139465
Epidemiol Infect. 2008 Jul;136(7):943-52
17678555
JAMA. 2005 Jun 8;293(22):2767-75
15941807
N Engl J Med. 1999 Oct 14;341(16):1174-9
10519895
Arch Intern Med. 2007 Feb 26;167(4):335-42
17325294
Lancet Infect Dis. 2005 Oct;5(10):629-36
16183517
Bull World Health Organ. 2003;81(3):217-21
12764518
JAMA. 1994 Mar 2;271(9):698-702
8309034
Respirology. 2006 Jul;11(4):442-8
16771914
Am J Epidemiol. 2008 Jun 15;167(12):1486-94
18400769
Lancet Infect Dis. 2003 Oct;3(10):624-32
14522261
Lancet. 1999 Mar 20;353(9157):1000-1
10459926
PLoS Med. 2008 Oct 28;5(10):e200
18959470
Epidemiol Infect. 1997 Oct;119(2):183-201
9363017
Am J Respir Crit Care Med. 2007 Jan 1;175(1):75-9
17038659
Epidemiol Infect. 2002 Aug;129(1):147-53
12211582
Tuber Lung Dis. 1996 Oct;77(5):391-400
8959141
Nat Med. 1995 Aug;1(8):815-21
7585186
Emerg Infect Dis. 2005 Apr;11(4):597-602
15829200
Lancet Infect Dis. 2003 May;3(5):282-7
12726976