Investigating the spatiotemporal links between the EVD outbreaks in Likati (2017) and Eastern DRC (2018–2020): a retrospective transdisciplinary study

Ebola virus (EBOV) outbreaks have occurred repeatedly in the Democratic Republic of the Congo (DRC), which can be grouped into three geographic clusters by phylogenetic lineage. This study investigates whether the EBOV outbreaks in Likati district (2017) and Ituri/North Kivu provinces (2018–2020) are linked by the movement of survivors, exploring the hypothesis that survivor mobility contributed to the tenth EBOV outbreak in Ituri/North Kivu. We conducted a retrospective, transdisciplinary study from April 2022 to May 2023, integrating anthropological fieldwork, interviews, and molecular and serological analyses. Using snowball sampling, we identified survivors and contacts who traveled from forest villages in Likati district to the Eastern DRC between July 2017 and May 2018, and not later than August 2018, when the tenth EBOV outbreak in North Kivu/Ituri was officially declared. Serological testing for Ebola antibodies and molecular analysis of semen samples were performed to detect past infections. One survivor from the Likati outbreak was identified who traveled to the mining village of Badengayido in Ituri Province in early 2018. The sperm test using GeneXpert® was negative for Orthoebola zairense virus (EBOV). Serological analysis confirmed a past Ebola infection. No other survivor or contact from the Likati outbreak was found to have traveled to Eastern DRC before the tenth EBOV outbreak. The survivor’s mobility patterns suggest a possible scenario for considering the tenth EBOV outbreak in Ituri and North Kivu provinces (2018–2020) as a resurgence from the 2017 outbreak in Likati. This study highlights the role of survivor mobility in the transmission of EBOV between outbreaks, with implications for outbreak surveillance and response. It underscores the need for improved methods to study the movement of survivors and contacts and for improved post-outbreak monitoring of asymptomatic survivors to prevent resurgence in vulnerable regions.