The serology of Ebolavirus – a wider geographical range, a wider genus of viruses or a wider range of virulence?

Abstract

Viruses of the genus Ebolavirus are the causative agents of Ebola virus disease (EVD), of which there have been only 25 recorded outbreaks since the discovery of Zaire and Sudan ebolaviruses in the late 1970s. Until the west African outbreak commencing in late 2013, EVD was confined to an area of central Africa stretching from the coast of Gabon through the Congo river basin and eastward to the Great Lakes. Nevertheless, population serological studies since 1976, most of which were carried out in the first two decades after that date, have suggested a wider distribution and more frequent occurrence across tropical Africa. We review this body of work, discussing the various methods employed over the years and the degree to which they can currently be regarded as reliable. We conclude that there is adequate evidence for a wider geographical range of exposure to Ebolavirus or related filoviruses and discuss three possibilities that could account for this: (a) EVD outbreaks have been misidentified as other diseases in the past; (b) unidentified, and clinically milder, species of the genus Ebolavirus circulate over a wider range than the most pathogenic species; and (c) EVD may be subclinical with a frequency high enough that smaller outbreaks may be unidentified. We conclude that the second option is the most likely and therefore predict the future discovery of other, less virulent, members of the genus Ebolavirus.

Serological evidence of exposure to ebolaviruses in domestic pigs from Guinea

“…Interestingly, a few porcine sera in our study bound to GP of The discovery of BOMV and other filovirus RNA as well as filovirus specific antibodies in different bat species (He et al, 2015;Jayme et al, 2015;Negredo et al, 2011;Olival et al, 2013;Yang et al, 2017) supports the assumed circulation of as yet undiscovered filoviruses with unknown pathogenic potential. Consequently, these filoviruses have been discussed to account for detectable serological cross-reactivity against known ebolaviruses in asymptomatic humans living in regions with no record of previous EVD outbreaks (Formella & Gatherer, 2016;Kuhn & Bavari, 2017;Mulangu et al, 2018) as well as in pigs from Sierra Leone (Fischer et al, 2018) with no report of previous clinical disease. cross-reactivity between these ebolavirus species has been observed previously (Fischer et al, 2018).…”

Serologic Markers for Ebolavirus Among Healthcare Workers in the Democratic Republic of the Congo

“…It is not known whether seroreactivity to assays is related to EBOV exposure during the 2014 outbreak-in particular because all HCWs included for this analysis participated in the outbreak response and reported varying levels of contact with EVD patients and biological specimens. It may also be possible that variation in antigenic response and neutralization levels may be related to asymptomatic or minimally symptomatic infection, which would not have been necessarily detected as illness due to EBOV [44]. It is possible that some seroreactive individuals could also have been exposed to a non-EBOV filovirus.…”

Serological Detection of Ebola Virus Exposures in Native Non-human Primates of Southern Nigeria

“…Their report is the only peer-reviewed evidence of the occurrence of human exposures to filoviruses in the country prior to July 2015. However, antibodies to these viruses have been detected in sera of human and NHPs, even in regions such as Ethiopia, Madagascar, Chad, Kenya, Zimbabwe [12] and Cameroon [13], where the clinical disease has not been previously observed. This has raised speculations about the actual geographical range of the disease in wildlife [12,13].…”