The West African Ebola virus disease (EVD) outbreak was the largest in history. The vast majority of cases were reported in Guinea, Sierra Leone and Liberia. Altogether, 28 646 people were infected and 11 323 died. 1 One of the explanations for the extent of the outbreak was the lack of response of local health systems. These health systems were incapable of responding adequately to the outbreak due to a lack of human resources, information, research, supply of medical products, financing and governance. 2 The devastating effect of the Ebola outbreak stretched far beyond the number of Ebola cases, and resulted in the deterioration of the provision and utilisation of routine health care. On the one hand the EVD outbreak compromised the functioning of the health system, due to the deaths of many health care workers and the closure of health facilities, 3,4 while at the same time communities had little trust in the capacity of providers to secure safe health care. In Ebola-affected communities many individuals feared to seek care, even for curable conditions. 4,5 The manner in which the provision and utilisation of programmes were affected by the outbreak was difficult to monitor during the outbreak response, given the state of emergency. All the attention of national and international health care providers was focused on limiting further spread of EVD, and reducing mortality in infected patients. We therefore studied in retrospect the effect of the Ebola outbreak on health system performance. Two Structured Operational Research Training Initiative (SORT IT) courses were organised, one in Liberia and one in Sierra Leone. The participants, the first authors of the manuscripts included in this supplement, were involved in the local health programmes during the Ebola outbreak. Course participation was defined as successful if the participant submitted a scientific manuscript to a peer-reviewed journal by the end of the course. 6 Sixteen studies were conducted, and are assembled here for this special issue. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Through the study of routine data the performance of a wide range of programmes was assessed before, during and after the outbreak. These studies present data from mother and child health care services, the human immunodeficiency virus (HIV), tuberculosis, vaccination, malaria, malnutrition and non-communicable diseases programmes. In addition, infection prevention monitoring, community health worker programme and performance-based financing are included.The different studies illustrate how service delivery and utilisation of most programmes dropped significantly during the Ebola outbreak. The greater the area affected, the sharper the decline, and the longer it took for performance to recover to pre-Ebola levels. The level of programme performance pre-Ebola also affected recovery post-Ebola. For example, in Liberia the already struggling immunisation programme was further weakened during the outbreak and took significant time to recover post-Ebola. 19 Ne...