The epidemiology of tuberculosis in South Africa

Early clinical descriptions oftuberculosis amongst the Black and Khoi San peoples emphasized the acute nature of the disease in those exposed to tuberculosis for the first time; there was much discussion of'virgin populations' and their implications for the spread and clinical features of tuberculosis (Cummins 1929). By 1920 observers in Black rural areas considered that tuberculosis had now begun to show certain 'endemic' characteristics and was no longer so acute or extensive in its features. Tuberculin testing in Black rural 'homelands' now found approximately 70% of the population to be infected, with 25—60% of children giving a positive reaction by age 10 years (Tuberculosis Research Committee of the Transvaal Chamber of Mines 1932). While this process unfolded, the incidence of tuberculosis amongst the southern African Caucasian population declined as in their countries of origin. Despite continual (and excessive) introduction of new infectious sources in the form of tuberculosis sufferers in search of 'heliotherapy' and 'aerotherapy' this decline accelerated. Much of the above rests on anecdotal evidence. In 1921, however, official notification of infectious diseases, with its acknowledged deficiencies, became country wide and from 1921 three periods can be identified:

(1) From a rate of 43 per 100 000 the incidence rose gradually to a peak of 365 per 100 000 in 1958, the latter stages of this increase being probably stimulated by the availability of chemotherapy.

(2) A period of declining incidence to a low of 162 per 100 000 in 1986. Part of this decline can, no doubt, be ascribed to the artificial exclusion of Black 'homelands' from the figures.

(3) A period of rising incidence reaching 226 per 100 000 in 1993; and it is on this rising arm which we now find ourselves.

This single notification figure obscures regional and racial differences and other anomalies such as sex- and age-related variations in rates.

Figure 1 shows the age- and gender-related notification rates in 1993 (Kustner 1995a). The features are not unexpected in a country with a high incidence of tuberculosis. Thus, high rates with a slight male predominance are experienced in early childhood, relatively low rates during ages 5—15 years ('the golden age of tuberculosis'), a sharp increase in adolescence with a female predominance and from approximately age 25—30 years considerably higher rates in males (Styblo 1991).

Table 1 summarizes the 1993 tuberculosis incidence rates for the four major South African racial groups (Kustner 1995a). The notified incidence of 20 and 11 for Caucasian males and females, respectively, stands in stark contrast to rates of 680 and 500 for Coloured males and females. The majority of the Coloured population reside in the Western Cape Province, and the Western Cape tuberculosis rates are a major point of discussion in South Africa. It should also be noted that a high tuberculosis prevalence (>3000 per 100 000) was recently documented amongst the Khoi San of Namibia (Nel & de Villiers 1993).

In 1989 the tuberculosis incidence in the Western Cape Province was 491 per 100 000 and 141 per 100 000 in the rest of South Africa (Kustner 1991). Not only

>1 5-9 15-19 25-29 35-39 45-49 55-59 65-69 >70 Age (years)

>1 5-9 15-19 25-29 35-39 45-49 55-59 65-69 >70 Age (years)

FIG. 1. Age- and gender-specific incidence of tuberculosis for South Africa in 1993. Data from Kustner (1995a).

were incidence rates approximately threefold higher than those in the rest of South Africa, but they also rose more sharply during adolescence. Thus, the incidence rates in the Western Cape Province in the age groups 10-14, 15—19 and 20—24 years were, respectively, 77, 273 and 585 per 100 000; whereas those in the rest of South Africa were, respectively, 42, 69 and 132 per 100 000. Evidence of the serious nature of the tuberculosis situation is also provided by the high rates of tuberculous meningitis in the Western Cape (Berman et al 1992). In 1985—1987 the age-specific incidence rates of tuberculous meningitis for the age groups < 1 year, 1—4 years, 5— 9 years and 10—14 years were, respectively, 31.5, 17.1, 4.8 and 0.7 per 100 000. Furthermore, age-specific incidence rates of pulmonary tuberculosis for the Coloured population, calculated by five-year birth cohorts, predict a persistent rise, despite a low incidence of HIV seropositivity at the time of the calculation:

TABLE 1 Race and sex-specific tuberculosis incidence rates (per 100 000 people) in South Africa in 1993

Black

Coloured

A sian

Caucasian

Male

242

680

58

20

Female

137

500

34

11

Data from Küstner (1995a).

Data from Küstner (1995a).

<1% seropositivity amongst pregnant women anonymously screened (Department of National Health and Population Development 1992).

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