Transmissibility and pathogenicity of Ebola virus: a systematic review and meta-analysis of household secondary attack rate and asymptomatic infection
This systematic review includes a meta-analysis of data about Ebola virus (EV) transmission in households and presents estimates of the asymptomatic proportion of the virus from serosurveys, using data from outbreaks mostly before the 2013 to 2016 West African outbreak.
Of nine studies included, there was no evidence of a significant difference in secondary attack rate (SAR) between EV subtypes, but a significant inverse relationship was found between outbreak year and household SAR for reports between 1976 and 2014. In the absence of direct patient contact, very little EV transmission occurred, and risks seem highest for those providing direct care.
The proportion of infections leading to asymptomatic illness, otherwise known as the subclinical/ asymptomatic proportion, is not clearly understood. The literature was reviewed for information from serosurveys measuring EV-specific antibodies,