Ecological Contexts of Index Cases and Spillover Events of Different Ebolaviruses

Abstract

Ebola virus disease afflicts both human and animal populations and is caused by four ebolaviruses. These different ebolaviruses may have distinct reservoir hosts and ecological contexts that determine how, where, and when different ebolavirus spillover events occur. Understanding these virus-specific relationships is important for preventing transmission of ebolaviruses from wildlife to humans. We examine the ecological contexts surrounding 34 human index case infections of ebolaviruses from 1976–2014. Determining possible sources of spillover from wildlife, characterizing the environment of each event, and creating ecological niche models to estimate habitats suitable for spillover, we find that index case infections of two ebolaviruses, Ebola virus and Sudan virus, have occurred under different ecological contexts. The index cases of Ebola virus infection are more associated with tropical evergreen broadleaf forests and consuming bushmeat than the cases of Sudan virus. Given these differences, we emphasize caution when generalizing across different ebolaviruses and that location and virus-specific ecological knowledge will be essential to unravelling how human and animal behavior lead to the emergence of Ebola virus disease.

Translating Predictions of Zoonotic Viruses for Policymakers

“…No occurrence data from Cameroon were used to make these predictions and all three overlapped in the tropical rainforest of the East region of Cameroon, with some predictions extending into the Central and South regions (Peterson et al 2004;Pigott et al 2014;Judson et al 2016). The tropical rainforest identified in the models is similar to where most EBOV index cases have occurred (Judson et al 2016). National experts agreed that this region might be at risk for EBOV spillover, but also acknowledged that long-distance movements by bats could put other areas at risk.…”

“…A qualitative dis- (Randolph and Rogers 2007), magenta . Ebola virus: yellow (Pigott et al 2014), magenta (Judson et al 2016), blue (Peterson et al 2004). Lassa virus: yellow (Fichet-Calvet and Rogers 2009) (model 2), magenta (Fichet-Calvet and Rogers 2009) (model 3), blue .…”

“…However, human index cases of EVD have been identified near the southern Cameroon border in the Republic of Congo and Gabon (Judson et al 2016). EBOV is one of the five ebolaviruses in the family Filoviridae.…”

“…The four other ebolaviruses are Sudan virus (SUDV), Tai forest virus (TAFV), Bundibugyo virus (BDBV), and Reston virus (RESTV). EBOV, SUDV, TAFV, and BDBV are known to spillover from wildlife and cause EVD in humans, while RESTV is not considered to be a human pathogen (Judson et al 2016). Three species of fruit bats have been found to be polymerase chain reaction (PCR) positive for EBOV (Leroy et al 2005), while other animals have been implicated as secondary hosts (Olival and Hayman 2014).…”

“…We obtained three publications with predictions for EBOV (Peterson et al 2004;Pigott et al 2014;Judson et al 2016). No occurrence data from Cameroon were used to make these predictions and all three overlapped in the tropical rainforest of the East region of Cameroon, with some predictions extending into the Central and South regions (Peterson et al 2004;Pigott et al 2014;Judson et al 2016).…”