Molecular Evidence of Sexual Transmission of Ebola Virus

Abstract

A suspected case of sexual transmission from a male survivor of Ebola virus disease (EVD) to his female partner (the patient in this report) occurred in Liberia in March 2015. Ebola virus (EBOV) genomes assembled from blood samples from the patient and a semen sample from the survivor were consistent with direct transmission. The genomes shared three substitutions that were absent from all other Western African EBOV sequences and that were distinct from the last documented transmission chain in Liberia before this case. Combined with epidemiologic data, the genomic analysis provides evidence of sexual transmission of EBOV and evidence of the persistence of infective EBOV in semen for 179 days or more after the onset of EVD. (Funded by the Defense Threat Reduction Agency and others.).

Figure 1. Clinical Timelines for the Patient and the Survivor, from September 2014 through May 2015

Shown are key dates regarding the Ebola virus disease (EVD) presentation, diagnostic tests, and outcomes for the survivor (S) and the patient (P). Horizontal bars estimate the number of days of persistence of the Ebola virus (EBOV) since the date of disease onset and since the date of clearance from blood. ETU denotes Ebola treatment unit.

Figure 2. Median-Joining Haplotype Network

This network was constructed from a full genome alignment of 100 clinical sequences of the Ebola virus Makona variant, including those assembled from blood samples obtained from the patient (P), the survivor’s older brother (SB), and the survivor’s former wife (SFW), from a semen sample from the survivor (S), and from 96 additional genomes chosen from the 796 genomes that were analyzed to be representative of samples collected in Guinea, Liberia, Mali, and Sierra Leone. For visual clarity, the network was limited to 100 genomes. The GenBank accession numbers for the tested genomes are as follows: for P, the number is KT587343, for S, the number is KT587344, for SB, the number is KT587346, and for SFW, the number is KT587345. Each colored vertex represents a sampled viral haplotype. The vertex size is proportional to the number of sampled sequences. Genomes sequenced in this study are shown in pink. Purple vertexes (SPB) indicate samples from the last known cluster of EVD cases in Liberia before the infection of the patient discussed in this report. Other colors indicate the respective countries of origin. Edges are not drawn to scale; hatch marks indicate the number of substitutions along each edge. The vertex SL2 represents the ancestral haplotype that is thought to have been introduced into Liberia in the spring of 2014.^,