Asymptomatic COVID-19 in South Africa - implications for the control of transmission

Asymptomatic COVID-19 may contribute significantly to the pandemic trajectory based on global biological, epidemiological and modelling evidence. A retrospective analysis was done to determine the proportion of asymptomatic COVID-19 in the workplace during the lockdown period from 27 March to 31 May 2020. We found that nearly 45% of cases were asymptomatic at the time of the first test. This high proportion of asymptomatic COVID-19 cases has implications for interventions, such as enforcing quarantine of all close contacts of COVID-19 cases regardless of symptoms.

Hard choices: Ethical challenges in phase 1 of COVID-19 vaccine roll-out in South Africa

Access to COVID-19 vaccines has raised concerns globally. Despite calls for solidarity and social justice during the pandemic, vaccine nationalism, stockpiling of limited vaccine supplies by high-income countries and profit-driven strategies of global pharmaceutical manufacturers have brought into sharp focus global health inequities and the plight of low- and middle-income countries (LMICs) as they wait in line for restricted tranches of vaccines. Even in high-income countries that received vaccine supplies first, vaccine roll-out globally has been fraught with logistic and ethical challenges. South Africa (SA) is no exception. Flawed global institutional strategies for vaccine distribution and delivery have undermined public procurement platforms, leaving LMICs facing disproportionate shortages necessitating strict criteria for vaccine prioritisation. In anticipation of our first consignment of vaccines, deliberations around phase 1 roll-out were intense and contentious. Although the first phase focuses on healthcare personnel (HCP), the devil is in the detail. Navigating the granularity of prioritising different categories of risk in healthcare sectors in SA is complicated by definitions of risk in personal and occupational contexts. The inequitable public-private divide that characterises the SA health system adds another layer of complexity. Unlike other therapeutic or preventive interventions that are procured independently by the private health sector, COVID-19 vaccine procurement is currently limited to the SA government only, leaving HCP in the private sector dependent on central government allocation. Fair distribution among tertiary, secondary and primary levels of care is another consideration. Taking all these complexities into account, procedural and substantive ethical principles supporting a prioritisation approach are outlined. Within the constraints of suboptimal global health governance, LMICs must optimise progressive distribution of scarce vaccines to HCP at highest risk.

Enzyme-linked immunospot assay responses to early secretory antigenic target 6, culture filtrate protein 10, and purified protein derivative among children with tuberculosis: implications for diagnosis and monitoring of therapy

BACKGROUND

The ability to detect tuberculosis-specific lymphocytes by enzyme-linked immunospot (ELISPOT) assay may have important implications for the diagnosis and monitoring of tuberculosis in children, for which routine methods lack sensitivity. We conducted a study to determine the presence and time course of ELISPOT responses in children with tuberculosis.

METHODS

Blood samples were obtained from children with a clinical diagnosis of tuberculosis, and interferon-gamma ELISPOT assays were performed using purified protein derivative (PPD), early secretory antigenic target 6 (ESAT-6), and culture filtrate protein 10 (CFP10) as stimulants. A subset of children were retested after 1, 3, and 6 months of therapy.

RESULTS

Detectable responses to ESAT-6 or CFP10 were found in 49 of 70 children with clinical tuberculosis but were more frequently found in those with culture-proven disease (P = .05). The number of subjects with responses to PPD increased after 1 month of therapy (P = .0004) and decreased at 3 and 6 months.

CONCLUSION

Tuberculosis-specific ELISPOT testing is a promising tool that should be evaluated as a potential diagnostic test for childhood tuberculosis. We caution against the use of an early decrease in response as a marker of successful antituberculous chemotherapy.

Long-term changes in the woody vegetation of the Kruger National Park, with special reference to the effects of elephants and fire

As part of the investigation reviewing the South African National Parks policy on the management of elephants in the Kruger National Park in South Africa it was decided to assess the current density and structural diversity of the woody vegetation in the park as it is affected by elephants and fire. The management policy used till recently, limited the population to approximately 7000 elephants, based on a conclusion that 6000 elephants (1 per 1.94 km2) was the highest number of elephants that could be carried in the Kruger National Park. The inclusion of the effects and interaction of fire in the investigation arises from the general recognition that elephants and fire can have a highly significant impact on the species and structural diversity of tree and shrub vegetation in African savannas. In the absence of quantitative data describing the condition of the woody vegetation in the Kruger National Park, subjective comparisons of changes in the density of large trees were made for the periods 1940 vs 1960 and 1960 vs 1986/89 using aerial photographs based on four of the major vegetation landscape units in the park. The results indicate that in the vegetation landscapes in areas with granitic soils there were no significant changes in the density of large trees between 1940 vs 1960 whereas a moderate decline occurred in the vegetation in the areas with basaltic soils. Conversely during the period 1960 to 1986/89 there was a dramatic decline in the density of large trees in all four major vegetation landscape units. On-site inspections and botanical surveys suggest that the decline in the density of large trees is the result of the effects of the interaction of elephants and fire. This had arisen because during the period 1960 to 1986/89 systematic burning programs had been introduced at the same time as elephant numbers had risen sharply. The results presented suggest that the changes in the woody vegetation do not involve a decrease in species diversity but rather a change in structural diversity where the woody vegetation is being transformed into a short woodland community interspersed with a low density of large trees. It is concluded that if it is desirable to prevent further structural changes to the woody vegetation then the current density of elephants should not be allowed to increase, the frequency of burning should be significantly reduced and the ignition procedure altered to allow or simulate point ignitions of fires.