Background

Since 2000, the world has seen unprecedented progress against the burden of malaria following massive investments in providing effective prevention and treatment interventions to populations at risk in malaria-endemic countries.

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Malaria case incidence declined by 30%, from 80 per 1000 population in 2000 to 57 per 1000 population in 2018. During the same period, the malaria mortality incidence rate declined by 60% – from 25 to 10 per 100 000 population at risk. By far, the majority of these gains have been due to reductions in the burden of malaria in sub-Saharan Africa (SSA), a region that still accounts for over 90% of malaria cases and deaths globally. These massive gains have been achieved despite important gaps in prevention and access to treatment, along with periods of conflict and other humanitarian emergencies. By all indications, however, the current COVID-19 pandemic will likely be the biggest threat faced by global efforts to reduce the malaria burden, especially in SSA where health systems are fragile.

The WHO Global Malaria Programme (GMP) maintains a platform to track and analyse potential threats to malaria control and elimination (http://apps.who.int/ malaria/maps/threats/), including drug and insecticide resistance, Plasmodium falciparum histidine-rich protein (pfhrp2) deletions and the spread of new invasive mosquito species. GMP has also used modelling as a tool to guide potential interventions in response to these threats, including during public health emergencies.

For example, during the humanitarian crisis in Borno State (Nigeria), modelling was used to estimate the potential impact of different types of interventions. Based on this analysis, four rounds of age-targeted mass drug administration (MDA) were delivered by the local health authority and the WHO polio and health emergencies teams, reaching more than 1.2 million children under the age of 5. It was estimated that the MDA campaign prevented about 10 000 children from dying of malaria. A similar analysis performed following the Ebola crisis in West Africa demonstrated the utility of modelling both the threats to malaria service delivery and the impact of potential mitigating strategies for planning and decision-making, as well as to raise awareness among policy-makers.

The COVID-19 pandemic represents a new threat to malaria service delivery. As the virus begins to spread in malaria-endemic countries, including in SSA (3), their fragile health systems will likely be overwhelmed. Indeed, the recent Ebola outbreak in West Africa demonstrated that a sudden increase in demand for health services can lead to substantial increases in morbidity and mortality from other diseases, including malaria. In response to this threat, WHO GMP has recently released guidance to help countries ensure the maintenance of their malaria services in the context of the COVID-19 pandemic.

GMP has also been working with several modelling teams to analyse the potential impact on malaria burden of different service disruption scenarios. The outputs of these modelling exercises reinforce the message that country programmes and ministries of health must ensure the continuity of malaria prevention and treatment services during the response to COVID-19. The results of these analyses are presented in this document. It is important to note that this analysis does not consider the impact of disruptions to indoor residual spraying (IRS) and seasonal malaria chemoprevention (SMC).

Analysis

Malaria transmission seasonality

Using the modelling framework previously employed in WHO’s Global technical strategy for malaria 2016–2030 (5), normalized malaria incidence in cases per person per year was calculated for SSA countries, assuming 35 days between peak rainfall and peak malaria incidence (Fig. 1). The resulting information can be used to understand the timing of COVID-19-related service disruptions with respect to malaria transmission seasons and can assist programmes in determining the optimal timing for mitigation activities with respect to COVID-19-related service disruptions.

The analysis shows clear seasonality varying by country, but with a broad regional signal. Peak malaria transmission starts later in the year in West Africa than in East and Central African countries. For many of the Sahelian countries in West Africa that implement SMC, peak transmission is likely to be reached in September. If the spread of COVID-19 continues along its current trajectory, the peak malaria season in these countries is likely to overlap with COVID-19-related disruptions.