Despite scientific development to strengthen the health system to protect and promote human health, Sub-Saharan Africa (SSA) continues to be confronted by longstanding, emerging, and remerging infectious disease threats [1, 2]. The region is particularly vulnerable to infectious disease epidemics because of its favourable climatic and ecological conditions for harbouring pathogens and their vectors in an environment with high human and animal interactions [3, 4]. Migration of wild animals and birds, frequent uncontrolled movements of people, commodities, animals and animal products across the national and international borders pose additional threats in the spread of infectious diseases . Moreover, civil unrest, improved communication and several socio-determinant factors have been associated with the spread of emerging infectious diseases in Africa [6–8]. Unfortunately, the region has a relatively low capacity for risk management of disease epidemics, mainly due to inadequate resources for early detection, identification, and prompt response . The failure in the early detection and response to epidemics in SSA is attributed to several factors, including deficiency in the development and implementation of surveillance and response systems against infectious disease outbreaks .
Disease surveillance is defined as the ongoing, systematic collection, analysis, interpretation, and dissemination of data about health-related events for use in public health action to reduce morbidity and mortality and to improve health [11–14]. It serves as an early warning system in identifying emerging and re-emerging health problems, assessing their trends, evaluating the impact of existing interventions, innovating and developing new public health interventions, properly allocating health resources, identifying risk factors and high-risk populations, and supporting public health research . Effective disease control requires prompt and adequate action towards the reduction or elimination of existing conditions and preventing the occurrence of new ones. Such actions can best be made when correct epidemiological and socio-ecological information reaches those required to act timely. Therefore, a functional surveillance system is critical in providing information for action on priority health events, including infectious disease epidemics .
Before 1998, infectious disease surveillance systems in most African countries were implemented through vertical programmes of specific diseases of national and /or international priority. Epidemiological data were collected by various programmes mainly at health care facility levels and in outreach health service settings . This situation led to fragmented and inefficient disease monitoring systems. As a potential solution, in 1998, the member states of the World Health Organisation (WHO) Regional Committee for Africa adopted a strategy namely, Integrated Disease Surveillance (IDS), with the intent to create and implement a comprehensive integrated, action-oriented, district-focused public health surveillance for African countries [17, 18]. To emphasize the critical linkage between surveillance to public health action and response, in 2001 the strategy was renamed as Integrated Disease Surveillance and Response (IDSR) [19, 20]. The IDSR strategy was developed in response to an increased frequency of emerging and re-emerging diseases causing high morbidity and mortality in African during the 1990s [17, 21]. Specifically, the strategy aimed to: i) integrate vertical disease surveillance systems for effective and efficient use of resources; (ii) improve the flow and use of information for detecting and responding to public health threats; and (iii) improve country capacity to detect and respond to priority public health events [17, 22].
During the past 20 years, the IDSR framework has been used in 44 (94%) of the 47 countries in the WHO African region to enhance capacity on surveillance for priority diseases, conditions, and events [23–25]. Nevertheless, each national IDSR strategy defines its disease priorities, administrative processes and key actors . IDSR functions are categorized into core and support functions. The core functions include identification of cases, investigation and confirmation, registration, notification/reporting the cases, data analysis and interpretation, response to the situation, communication and provision of two-way feedback, evaluation of the intervention and prepare for emergency occurrences and are implemented at all levels of the health system . The support functions include guidelines, laboratory capacity, supervision, training, resources and coordination at all levels of the health system [22, 23].
In most African countries the strategy has been implemented for about two decades and the number of priority diseases required for reporting has changed and increased . Factors associated to the increase include epidemiological and non- epidemiological such as social, economic, and environmental changes [26, 27]. This was also done to leverage the purpose and scope of the International Health Regulations 2005 . Having large number of diseases monitored by the public surveillance system creates implementation challenges due to the low laboratory capacity to diagnose diseases and low utilization of primary health-care system, hence unconfirmed and incomplete data generated by the conventional system. In addition, the African continent has recently experienced major epidemics including those of Ebola virus disease, dengue fever, cholera, yellow fever and coronavirus disease 2019 which spread faster and further due to high global connectivity, slow detection, and might easily missed by the routine monitoring systems.
Over the years, the IDSR has relied heavily on the routine health information system implemented at the facility and district levels of the health systems . However, technology advancement and new platforms for communication such as social and news media are growing in Africa; bringing more opportunities on availability, innovating and incorporating digital data into surveillance information, to compliment the passive facility-based surveillance. Since its adoption in SSA, the effectiveness and performance of IDSR in the region and specific country has been studied by a number of authors focusing on its functions, however, assessment on the how the challenges and opportunities coming with IDSR evolvement, technology expansion and availability of other data sources relevant for detecting and managing epidemics has not been documented with certainty. The objective of this systematic review was to analyse how IDSR implementation has embraced advancement in information technology, big data analytics techniques and wealth of data sources to strengthen detection and management of infectious disease epidemics in SSA. The gaps, challenges and opportunities identified are used to propose appropriate strategies to improve surveillance in the region.