National Tuberculosis Prevalence Survey (2013-14)

Abstract

Globally, 6.1 million cases of tuberculosis (TB) were notified in 2013; of which 93% (5.7 million) were newly diagnosed and 6.5% (0.4 million cases) were already on treatment (WHO 2014). WHO estimates that at least 3 million cases are “missed cases” that are either not detected or not notified on national TB programmes in the year 2013. This calls for improved case detection and notification in order for all cases to be properly treated and under adequate TB care.

Zambia, with a population of about 14.5 million people is one of the countries experiencing high TB notification rates which in 2010 were reported to be at 365 per 100,000 population for all ages (Kapata et al 2011). There has been an increase in TB notification rates from 216 per 100,000 population in 1990 to 524 per 100,000 population in 2004 and thereafter the notification rates have been declining steadily (Kapata et al 2011). Furthermore, since 1984 with the advent of HIV pandemic, Zambia has experienced a fourfold increase in TB case notification rates. Other factors which are exacerbating the TB burden in Zambia include high poverty levels, poor housing (CSO 2011), limited TB control strategies in congregate settings (O’Grady et al 2011) and challenges with diagnosing TB in paediatric patients (Chintu et al 2004, Mwaba et al 2011).

The disease burden varies among provinces. The highest notification rates are reported from Lusaka, followed by Copperbelt and Southern Provinces. The higher notification rates are consistent with regions along the line of rail while the lowest rates of notifications are from provinces off the line of rail (MoH TB Program Report 2011). This distribution is similar to that of the HIV prevalence rates in the country. This information is drawn from the fact that HIV is a strong predisposing factor fuelling the TB infection in sub-Sahara Africa (Godfrey-Faussett 2002, WHO 2011). In Zambia, 50-70% of TB patients are co-infected with HIV (MoH 2008, MoH TB Program Review Report 2011; Kapata et al., 2013).

The hallmark of TB control is early case detection and treatment which is promoted by direct observed treatment -short course (DOTS) strategy. Evaluation of the performance of the National TB control program is measured by aligning national targets and indicators with recommended global targets and indicators. The high TB burden in Zambia has moved TB control from hospital to community-based programs (Godfrey-Faussett 2002, MoH TB Program Review Report 2011), thereby creating the need for an alternative approach to assessment of disease prevalence in the population and impact assessment of interventions.

The estimates of TB burden in Zambia rely on TB notification data and WHO annual estimates derived from passive case finding and epidemiological models. In order to determine population -based estimates for pulmonary TB in the population aged 15 years and above and define a baseline to evaluate the impact of TB control programs in the future, a national prevalence survey was conducted from 2013-2014.