In December 2019, an outbreak of a new disease named COVID-19, caused by a novel coronavirus known as SARS-Cov2, appeared in Wuhan, China [1]. COVID-19 has spread rapidly around the world. About 213 countries are currently affected and 2,549,632 cases and 175,825 deaths have been confirmed worldwide [2]. On 2 March 2020, Senegal registered its first confirmed case of SARS-Cov2 that had been imported from France. On 2 May 2020, the number of confirmed cases went up to 1115, including 161 in the holy city of Touba, in the region of Diourbel, where the Grand Magal of Touba (GMT) is celebrated [3].

The GMT is the largest Muslim Mass Gathering (MG) in Africa between 4 and 5 million pilgrims each year estimated to celebrate the departure into exile of the Cheikh of the Mouride community, who was deported to Gabon by the French authorities in 1895 [4]. The context of the GMT is unique in Africa (Figure 1). Over the course of 1 week, it brings together several million people, in a limited geographical area (the holy city of Touba and its outskirts). On the occasion, pilgrims from all Senegal and even from abroad, flock to this city using all available means of transport, with all the attendant risks of road accidents. These people are of all ages: children under five, teenagers, young and old men and women, elderly people, in varying states of physical health and from all social and economic strata. During the GMT, the total population of pilgrims is six times the usual population of Touba according to data collected during the 2005 cholera outbreak, based on mobile phones belonging to people travelling to Touba from all over the country [5]. A pilot study conducted in 2017 among GMT pilgrims from the villages of Dielmo and Ndiop showed that 41.8% of participants reported respiratory symptoms, and an acquisition of rhinovirus (13.0%), coronavirus (16.0%) and adenovirus (4.6%) [6]. Finally, a prevalence of influenza infections (42.3%) higher than in any other studies conducted in Senegal was reported in GMT patients [Unpublished data]. It is likely that the crowded conditions of the GMT encourage the transmission of influenza, as observed in other MG settings [7].

Figure 1

Grand Magal de Touba in 2019, the largest mass gathering in Senegal.

Mass gathering participants are often exposed to high risks of the increased transmission of infectious diseases, especially respiratory diseases [8]. The current COVID-19 pandemic poses serious public health challenges across the globe and experts have recommended cancellation of the Hajj pilgrimage to Mecca, which is planned in July early August 2020, and of the Tokyo Olympic Games, planned from 24 July to 9 August 2020 [9]. Human coronavirus circulation (notably 229E) has already been demonstrated at the Hajj and at the Olympic games [10,11].

Nevertheless, it is too early to consider cancelling the GMT, which is scheduled to take place from 5 or 6 October 2020, according to the Muslim calendar. It will be necessary to monitor the progress of the COVID-19 pandemic within Senegal and around the world [12]. If the GMT is maintained, it will be necessary to take very strict sanitary measures to limit the propagation of infectious disease, especially COVID-19. There is, therefore, an absolute need to set up effective surveillance, in particular epidemiological surveillance, to prevent all these risks, and more generally to ensure that the resident populations and pilgrims benefit from the monitoring needed to prevent the emergence of new diseases or the decompensation of pre-existing diseases. A good health surveillance system is evidently conditions upon on an adequate information system, with tools for collecting information. A good sanitary system must cover all these aspects. Senegal is a member of the WHO and has adopted the IHR (International Health Regulations) that governs the surveillance of large gatherings, which stipulates that infectious diseases must be reported in real time. The GMT is a source of health risks that must be detected and managed quickly and the emergence or the spread of communicable infectious diseases is the main risk. Due to the international dimension of the GMT, these diseases may even spread beyond borders.