Epidemiology of tuberculosis in a high HIV prevalence population provided with enhanced diagnosis of symptomatic disease.
BACKGROUND
Directly observed treatment short course (DOTS), the global control strategy aimed at controlling tuberculosis (TB) transmission through prompt diagnosis of symptomatic smear-positive disease, has failed to prevent rising tuberculosis incidence rates in Africa brought about by the HIV epidemic. However, rising incidence does not necessarily imply failure to control tuberculosis transmission, which is primarily driven by prevalent infectious disease. We investigated the epidemiology of prevalent and incident TB in a high HIV prevalence population provided with enhanced primary health care.


RESULTS
Twenty-two businesses in Harare, Zimbabwe, were provided with free smear- and culture-based investigation of TB symptoms through occupational clinics. Anonymised HIV tests were requested from all employees. After 2 y of follow-up for incident TB, a culture-based survey for undiagnosed prevalent TB was conducted. A total of 6,440 of 7,478 eligible employees participated. HIV prevalence was 19%. For HIV-positive and -negative participants, the incidence of culture-positive tuberculosis was 25.3 and 1.3 per 1,000 person-years, respectively (adjusted incidence rate ratio = 18.8; 95% confidence interval [CI] = 10.3 to 34.5: population attributable fraction = 78%), and point prevalence after 2 y was 5.7 and 2.6 per 1,000 population (adjusted odds ratio = 1.7; 95% CI = 0.5 to 6.8: population attributable fraction = 14%). Most patients with prevalent culture-positive TB had subclinical disease when first detected.


CONCLUSIONS
Strategies based on prompt investigation of TB symptoms, such as DOTS, may be an effective way of controlling prevalent TB in high HIV prevalence populations. This may translate into effective control of TB transmission despite high TB incidence rates and a period of subclinical infectiousness in some patients.
Corbett
Elizabeth L
EL
London School of Hygiene and Tropical Medicine, London, United Kingdom. elc1@mweb.co.zw
Bandason
Tsitsi
T
Cheung
Yin Bun
YB
Munyati
Shungu
S
Godfrey-Faussett
Peter
P
Hayes
Richard
R
Churchyard
Gavin
G
Butterworth
Anthony
A
Mason
Peter
P
D017088:AIDS-Related Opportunistic Infections / Q000150:complications* / Q000175:diagnosis / Q000453:epidemiology; D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D023801:Directly Observed Therapy; D005260:Female; D006801:Humans; D015994:Incidence; D007538:Isoniazid / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009786:Occupational Health Services; D015995:Prevalence; D012307:Risk Factors; D013183:Sputum / Q000382:microbiology; D014397:Tuberculosis, Pulmonary / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control; D015030:Zimbabwe / Q000453:epidemiology
D007538:Isoniazid