Public health-relevant consequences of the COVID-19 pandemic on malaria in sub-Saharan Africa: a scoping review

The emergence of SARS-CoV-2 in China by the end of 2019 has led to the largest pandemic in recent human history [1, 2]. By 14 June, 2021, there were some 176 million confirmed cases of COVID-19, including 3.8 million deaths, reported to the World Health Organization (WHO) [3]. The COVID-19 epidemic waves show variable dynamics in the different WHO Regions, with the highest burden in the American, European and Southeast Asian Regions [3, 4]. The latter has recently shown particularly high incidence rates, and India is now reporting the second highest number of confirmed cases after the USA [3]. In contrast, the African and the Western Pacific WHO Regions continue to report only relatively low numbers of cases and deaths [3, 4].

It was initially predicted that Africa would be the worst affected region by the COVID-19 pandemic because of its weak health systems, prevailing poverty and the high burden of other infectious diseases [5, 6]. However, by the end of 2020 about 3.5% of the global number of COVID-19 cases and deaths were reported from this continent, which is home to 17% of the world’s population [3, 7]. Overall, the epidemiology of COVID-19 in Africa remains puzzling [5]. By 14 June, 2021, there were some 3.6 million COVID-19 cases and 89,000 deaths reported from the entire continent, and most of these were from its northern and southern regions [8, 9]. Potential explanations for such a situation are incomplete data due to much lower testing capacities, a significantly younger population, overall lower population mobility, cross-reactive immunity or immunomodulation due to high prevalence of other infectious agents, and effects of public health responses [5, 7, 10]. First findings from SARS-CoV-2 seroprevalence surveys support the evidence for significant under-reporting and for a predominance of asymptomatic and mild cases [11, 12]. Nevertheless, it appears that the second epidemic wave has hit the African continent more severely than the first one, possibly explained by the emergence of more transmissible SARS-CoV-2 variants [7, 13].

Globally, malaria is still the most important parasitic disease and responsible for a quarter of all deaths among children under 5 years old in sub-Saharan Africa (SSA) [14, 15]. The efforts for global malaria control and elimination have achieved large successes during the last two decades, but progress has stalled in recent years, and the COVID-19 pandemic could largely reverse the overall trend [16, 17]. This review aims to summarize currently available data and understanding of the direct and indirect effects of the COVID-19 pandemic on the malaria burden in SSA.

Figure 2 visualizes the study selection process. The initial search produced 851 documents. After removal of 203 duplicates, 648 documents underwent title and abstract screening. After exclusion of 535 documents, which did not meet the inclusion criteria, 113 papers were included for full text review. Nine papers were added from reference screening; 71 were excluded as they also did not meet the inclusion criteria. Thus, a total of 51 papers were reviewed (6 modelling studies, 10 country reports, 6 general reports, 1 case report, 9 review papers, 18 opinion papers, and 1 policy guideline).

The COVID-19 pandemic has a massive impact on nearly all countries across the world. While the initial spread of SARS-CoV-2 to Africa has been slow and the COVID-19 burden appears to be much lower than in other continents, the pandemic carries a high potential to negatively affect the control of other diseases, such as malaria [7]. It has already been shown, that the pandemic has resulted in major reductions of incidence of other respiratory diseases due to various effects [66]. Moreover, it has been predicted that the pandemic will result in major disruptions of routine childhood vaccinations, which may cause an increase in vaccine-preventable infectious diseases in SSA [67]. Both malaria and COVID-19 affect disproportionally the low socio-economic classes [28, 32, 68]. It is possible that the COVID-19 pandemic and its indirect effects, including the measures to contain it, may produce collateral damage similar to those seen 6 years ago during the West African Ebola epidemic, i.e., a sharp increase of malaria deaths which finally exceeded the direct Ebola mortality [17, 36, 69]. Thus, understanding how the COVID-19 pandemic affects malaria control measures is of extreme importance for SSA [17, 59].

Accelerated malaria control efforts since the early twenty-first century have significantly reduced the malaria burden in Africa and worldwide [17]. Control strategies include ITN and IRS interventions, early diagnosis and rapid treatment with ACT, and intermittent preventive treatment for infants, children and pregnant women [14]. However, the rate of reduction in malaria morbidity and mortality in SSA has recently stalled, and the initial overall positive trend could be seriously reversed due to the effects of the COVID-19 pandemic as shown in several modelling studies [17, 21‐23].

In accordance with the conceptual framework, four major themes likely play an important role for the effects of the COVID-19 pandemic on malaria in SSA: (1) diagnostical and clinical aspects; (2) access to health care services; (3) availability of curative and preventive malaria commodities; and, (4) impact on malaria prevention programmes. While diagnostical and clinical aspects will play an obvious role due to the overlapping symptoms of both diseases [27, 70, 71], therapeutic aspects related to initial misperceptions regarding the efficacy of certain anti-malarials against COVID-19 may have been overemphasized [25, 36]. Co-infection with malaria may complicate COVID-19, while immunomodulation caused by previous malaria exposure may result in less severe COVID-19, as was previously also shown in other respiratory diseases [72‐75]. Reduced access to health care services due to direct and indirect effects of the pandemic has a negative impact on access to anti-malarial treatment, thus it would likely have a major effect on the malaria burden in endemic countries [17, 49, 53]. This will be compounded by the clear negative impact of the pandemic on global supply chains for curative and preventive malaria commodities [48, 52]. The consequences of the pandemic for preventive malaria control programmes have been much emphasized by many of the reviewed papers and particularly in modelling papers. However, as an effect of such early warnings, country programmes and funding for malaria have probably adapted rapidly to the pandemic as early as 2020, which may have reduced the modelled impact [28, 59]. International actors such as WHO may have contributed to the prevention of some worst-case scenarios by providing adapted malaria strategies and keeping malaria in their priorities [17, 30].

Until June 2021, only a few reports provided actual epidemiological data on malaria in SSA during the first wave of the pandemic in 2020, thus drawing conclusions on these data might be premature. However, these reports showed that the number of reported malaria cases in Sierra Leone, Uganda and the DRC, that are more highly malaria-endemic countries, was much lower than expected [29, 61‐63], while the number of reported malaria cases in Zimbabwe and Zambia, that are countries of low endemicity, was higher than in previous years [27, 29, 64, 65]. It could be speculated that possibly lower access to health care services in combination with impaired malaria surveillance systems may have led to a lower number of reported malaria cases and deaths in these selected highly endemic countries. In the two low-endemic southern SSA countries, disruption of malaria control activities within relatively well-functioning health systems, including surveillance activities, may have resulted in a higher number of reported malaria cases and deaths. More information from other African endemic countries is needed to fully assess such developments [59, 76]. As the COVID-19 pandemic is far from being under control in most low- and middle-income countries, as new and more infectious SARS-CoV-2 variants are emerging, and as SSA countries have limited access to COVID-19 vaccines, dramatic increases in the malaria burden may occur [59, 77, 78]. Although the findings of existing modelling studies are already alarming, the final impact of the pandemic on the malaria burden could be even more devasting [21, 51]. Better education, sensitization and de-stigmatization of both diseases is essential, including emphasis on early care-seeking behaviour, which also needs more community participation [25, 29]. Community health workers should be encouraged to treat all uncomplicated malaria cases in the community and to refer to health facilities only severe cases [51, 79]. As 2020 was a year with many planned malaria prevention campaigns, the negative effects of disrupted programmes would probably last for some years [21, 23]. Fortunately, the international community, including WHO, acted fast to counteract such developments [17]. However, there is the need for more support for SSA countries from the international community and from high-income countries [32]. Malaria, one of Africa’s deadliest diseases, which disproportionally affects the most vulnerable population groups, must be kept under control [16, 35, 59].

The findings from this review provide evidence for a significant but diverse impact of the COVID-19 pandemic on the malaria burden in SSA. Only results of further studies will enable a full understanding of these developments and its public health consequences. In the meantime, SSA countries need more support from the international community including the urgent delivery of COVID-19 vaccines for high-risk groups.