Variability in Intrahousehold Transmission of Ebola Virus, and Estimation of the Household Secondary Attack Rate.

Judith R Glynn,Hilary Bower,Daniel Sesay,Saidu H Mansaray,Sembia Johnson,Alie Joshua Kamara,Cecilia Turay,Osman Kamara,Francesco Checchi,Mohammed S Bangura

doi:10.1093/infdis/jix579

Abstract

Transmission between family members accounts for most Ebola virus transmission, but little is known about determinants of intrahousehold spread. From detailed exposure histories, intrahousehold transmission chains were created for 94 households of Ebola survivors in Sierra Leone: 109 (co-)primary cases gave rise to 317 subsequent cases (0-100% of those exposed). Larger households were more likely to have subsequent cases, and the proportion of household members affected depended on individual and household-level factors. More transmissions occurred from older than from younger cases, and from those with more severe disease. The estimated household secondary attack rate was 18%.

Highlights

Funerals and healthcare settings play an important role in the spread of Ebola virus, community transmission, mostly between family members, accounts for the majority of transmissions [1, 2]
Transmission chains were created for each household, based on the contact patterns described by the household members
We investigated whether any household transmission occurred, and the proportion of household members infected, by characteristics of the primary case(s) and the household

Summary

Introduction

Funerals and healthcare settings play an important role in the spread of Ebola virus, community transmission, mostly between family members, accounts for the majority of transmissions [1, 2]. In a study of 94 households of survivors, we have previously estimated exposure-specific and age-specific attack rates [4], risk factors for the acquisition of Ebola in young children [11], and the extent of asymptomatic infection [12]. In this analysis we reconstruct the likely within-household transmission chains to assess factors influencing transmission and who probably transmitted to whom; and estimate the household secondary attack rate, a key parameter for transmission modeling studies [13]

Methods

Results

Conclusion