“Reduce the number of new TB infections as well as deaths from TB by 50%” – a key target of the NSP 2012–2016

The first year of the five-year National Strategic Plan for HIV, TB and STIs (NSP), launched in December 2011, has come to an end. Now is an important time to reflect on what has been done so far to put the country on track to meet the NSP targets, especially in one of the plan’s key focus areas: tuberculosis (TB).

TB in South Africa is closely linked to HIV. More than 70% of people with active TB disease are also HIV-positive. By including TB in the current NSP, South Africa is seeking to improve the coordination and integration of the TB and HIV responses.

South Africa has the third highest TB burden in the world. Between 1993 and 2007, the number of cases tripled in South Africa from 305 to 948 per 100,000 people, and the mortality rates quadrupled. The latest national figures for TB mortality from 2010 show that the disease retained its top spot as the leading cause of natural death in the country, accounting for 11.6% of total deaths.

The current NSP seeks to reduce TB deaths. It has set a target of reducing the number of deaths of people who are diagnosed and initiated onto treatment by 50%. The NSP also recognises that many individuals with the disease are slipping through the cracks and are not being properly diagnosed and treated for TB.

To address this problem, the five-year-long NSP aims to screen 30 million people for TB. The plan further aims to increase the percentage of people with active TB who are properly diagnosed and initiated onto treatment to over 85%.

A review of figures from the Department of Health (DoH) shows that the scale-up of screening, diagnosis and treatment aimed at meeting these targets has been sluggish in the first year of the NSP. 2,600,925 people were screened for TB during 2012 – a reduction from 2,718,939 people screened during 2011.

According to the DoH, this decline occurred because using TB screening teams at a household level was not sustainable. The DoH is now absorbing their functions into primary health care ward-based teams. Meanwhile, the total number of patients diagnosed with drug-susceptible TB during 2012 is still being calculated.

The DoH has reported an increase in the number of patients diagnosed with multidrug-resistant TB (MDR-TB), following the rollout of the GeneXpert diagnostic system. But many South Africans with active MDR-TB are never diagnosed. Estimates suggest that up to 50% of all cases in 2011 may not have been diagnosed. As the distribution of GeneXpert machines has gained momentum during 2012, the DoH has registered an increase in MDR-TB diagnoses.

However, while the DoH has diagnosed more people with MDR-TB, it has failed to keep pace by scaling up treatment. The gap between the number of patients diagnosed with MDR-TB versus the numbers enrolled onto treatment widened between 2011 and 2012.

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Patients diagnosed with MDR-TB in 2011: 10,085. In 2012: 15,419

Patients enrolled onto treatment for MDR-TB in 2011: 5,634. In 2012: 6,800

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These figures show that the DoH’s efforts so far to scale-up TB screening, diagnosis and treatment have been slow. Greater momentum is now needed to help South Africa control the TB epidemic and civil society must closely monitor the progress of the DoH.

These figures for screening, diagnosis and treatment during 2013 are based on e-mail communication with the DoH on 13 May 2013. The DoH provided these figures but did not respond to requests for clarification and confirmation. The DoH should publicly release official figures for this period.

Have we set the right targets?

“The NSP Strategic Objective 2 aims to prevent TB infection and disease. This is to be achieved through intensified TB case finding, TB infection control, workplace/occupational health policies on TB and HIV, isoniazid preventive therapy (IPT), immunisation, prevention of multidrug-resistant TB (MDR TB), and reducing TB-related stigma, alcohol consumption and smoking” – From NSP Strategic Objective 2.

Professor Robin Wood is the Director of the Desmond Tutu HIV Centre. Wood and his colleagues have published multiple studies examining the risk of TB transmission in South Africa. Through his work, Professor Wood has gained immense insight into the risk of TB infection in settings such as public transport, prisons, townships and the wider context of the city of Cape Town.

When I met Professor Wood to discuss TB transmission in South Africa, I learnt about what he calls his ‘gadget’ for measuring TB risk. This portable gadget is in fact a continuous carbon dioxide sampling device which measures the amount of carbon dioxide that a person inhales in different environments. Carbon dioxide is a natural indicator of the amount of rebreathed air that a person inhales.

Wood explains that the high risk of TB infection facing South Africans is due to a number of environmental challenges. Professor Wood notes: “[The] risk of contracting TB is determined by the number of people one meets, the environment [one] meets them in, and how many of these people have active TB”.

Wood is currently using the gadget to identify which environments pose the highest TB infection risk for children. To do this, he and his colleagues have given the portable devices to children living in Western Cape townships. With GPSs attached, these gadgets measure the fraction of rebreathed air the children inhale as they go about their daily activities. Wood has already found that a child’s risk of contracting TB soars in poorly ventilated classrooms.

By the time they turn 18, more than 80% of South African children have been infected at least once with TB. According to Wood, setting stricter building standards to improve ventilation in classrooms could massively reduce new childhood cases of the disease.

Wood and colleagues have identified prisons and public transport as similarly high risk environments for contracting TB.

Having a TB infection is not the same as having active TB disease. But according to Wood, a review of the history of TB in South Africa and elsewhere reveals that curbing transmission is key to curbing cases of active TB and reducing TB mortality.

Wood describes how TB notifications in Europe and America dropped from 1,000 per 100,000 people in 1860 (levels similar to South Africa’s at that time) to 100 per 100,000 in 1960. He notes the massive, consistent drop in TB incidence over this 100-year period before the development and availability of effective medicines to treat TB. According to Wood, the massive decline in TB notifications in Europe and America was mainly due to improvements in building standards and ventilation.

Professor Wood argues that the NSP fails to focus properly on reducing TB transmission. He sees this as a major gap in the plan, noting that “transmission is key and we have to stop it”.

According to Wood, the failure of the NSP  to prioritise reducing transmission is largely due to the fact that the NSP targets originate from a WHO model which uses data from Europe. He explains that “the model makes assumptions that do not fit the South African context”. As a result its recommendations are inadequate for curbing the epidemic level of new TB cases in South Africa. “What we need is a South African solution developed from South African data.” According to Wood such a solution would place a much greater emphasis on the prevention of TB transmission.

 

Understanding TB risk

The NSP correctly seeks to improve the available evidence regarding the risks of contracting and/or developing active TB. However, there is an existing body of evidence regarding these risks on which we can act now. The infograms below provide a summary of key evidence regarding the risk of contracting and/or developing TB for a number of sub-populations in South Africa.

1. TB and HIV

A recent study conducted in Gugulethu in the Western Cape confirmed existing evidence that a person living with HIV who has spent time on ART has a significantly lower chance of developing active TB. The risk of TB incidence for people who are on ART and have CD4 counts below 100 is nine times higher than those who are on ART and have counts above 700. However, even people with HIV who have high CD4 counts continue to have a greater risk of developing active TB than those who are HIV-negative. The study found that TB incidence for patients who are on ART and have CD4 counts above 700, still remains four times higher than HIV-negative members of the same community.

 2.  TB and public transport

Using crowded public transport which does not have adequate ventilation raises the risk of contracting TB. A 2012 study employed a mathematical model to assess the risk of TB infection on Cape Town public transport by measuring the amount of rebreathed air. The study found that:

Daily bus commuters have a 3.5% risk of TB infection;

Daily train commuters have a 3.7% risk of TB infection;

Daily minibus taxi commuters have a 5% risk of TB infection.

 3. TB and mining

TB incidence is estimated to be five to six times higher among miners than in the general population.

The high rate of silicosis amongst gold miners means they have a particularly high risk of developing active TB. In gold-producing countries there is, on average, a 32.4% higher incidence of TB than in countries that do not mine the precious metal.

4. TB and prisons

A 2011 study used mathematical modelling to assess the risk of TB transmission in South African prisons. The study found that due to overcrowding, poor ventilation and failure to provide adequate outdoor time, the risk of TB infection is as high as 90% per annum. (This is the risk of contracting TB, not the risk of developing active TB.)

5. Lifetime risk of contracting TB in a high-prevalence South African city

For an HIV-negative person living in Cape Town, the lifetime risk of developing smear-positive pulmonary TB is approximately 10%.

The graph to the right shows the accumulated life-time risk of being notified with new or relapsed TB calculated for HIV-negative individuals. Values are based on cumulative 2009 age-specific TB notification rates for Cape Town.

By Catherine Tomlinson

 

Sources: DoH screening, diagnosis and treatment figures from e-mail communication on 13 May 2013; Gupta A, Wood R, Kaplan R, Bekker L-G, Lawn SD ‘Tuberculosis Incidence Rates during 8 Years of Follow-Up of an Antiretroviral Treatment Cohort in South Africa: Comparison with Rates in the Community.’ PLoS ONE 7(3): e34156. doi:10.1371/journal.pone.0034156 (2012); Stuckler D, Basu S, McKee M, Lurie M. ‘Mining and Risk of Tuberculosis in Sub-Saharan Africa.’ American Journal of Public Health Vol 101, No. 3  (2011); Johnstone-Robertson S, Lawn SD, Welte A, Bekker L-G, Wood R. ‘Tuberculosis in a South African prison – A Transmission Modelling Analysis.’ South African Medical Journal, Vol 101, No 11 (2011); Wood R, Lawn S, Johnstone-Robertson S, Bekker L-G. ‘Tuberculosis control has failed in South Africa – time to reappraise strategy.’ South African Medical Journal Vol. 101 No. 2 (2011); Andrews JR, Morrow C, Wood R. ‘Modeling the Role of Public Transportation in Sustaining Tuberculosis Transmission in South Africa.’ American Journal of Epidemiology Vol. 177 No. 6 (2013);  National Health Laboratory Services. Pathology Division Surveillance Report (2011); STATSSA. ‘Mortality and Causes of Death in South Africa 2010’ (2013);  WHO Global TB Control Report: South Africa Country Report (2012).