Ebola Virus Shedding and Transmission: Review of Current Evidence

Abstract

Background. The magnitude of the 2013-2016 Ebola virus disease outbreak in West Africa was unprecedented, with >28 500 reported cases and >11 000 deaths. Understanding the key elements of Ebola virus transmission is necessary to implement adequate infection prevention and control measures to protect healthcare workers and halt transmission in the community.Methods. We performed an extensive PubMed literature review encompassing the period from discovery of Ebola virus, in 1976, until 1 June 2016 to evaluate the evidence on modes of Ebola virus shedding and transmission.Findings. Ebola virus has been isolated by cell culture from blood, saliva, urine, aqueous humor, semen, and breast milk from infected or convalescent patients. Ebola virus RNA has been noted in the following body fluids days or months after onset of illness: saliva (22 days), conjunctiva/tears (28 days), stool (29 days), vaginal fluid (33 days), sweat (44 days), urine (64 days), amniotic fluid (38 days), aqueous humor (101 days), cerebrospinal fluid (9 months), breast milk (16 months [ preliminary data]), and semen (18 months). Nevertheless, the only documented cases of secondary transmission from recovered patients have been through sexual transmission. We did not find strong evidence supporting respiratory or fomite-associated transmission.

Recently Identified Mutations in the Ebola Virus-Makona Genome Do Not Alter Pathogenicity in Animal Models

“…Our data here support attenuation rather than adaptation of EBOV-Makona during the recent epidemic, as lower organ titers and weaker disease progression in IFNAR −/− mice (Figures 2, 3, and S1) as well as slightly prolonged disease progression and reduced virulence in rhesus macaques (Figures 4, 5, and S2–S5) were associated with animals infected with EBOV-Makona later 2014 clinical isolates (Mali and Liberia). However, we did not observe any difference in viral shedding from mucosal membranes, commonly used as an indirect measure for transmission (Gustin et al, 2013; Vetter et al, 2016), when macaques were infected with EBOV-Makona early or later 2014 isolates or with EBOV-Mayinga (Figure S6). This is in contrast to a previous study describing increased virus shedding associated with EBOV-Makona (C05 and C07) infection when compared to EBOV-Kikwit (Wong et al, 2016).…”

New and emerging infectious diseases (Ebola, Middle Eastern respiratory syndrome coronavirus, carbapenem-resistant Enterobacteriaceae, Candida auris): Focus on environmental survival and germicide susceptibility

“…[33][34][35] Environmental contamination and survival Ebola virus has been isolated by cell culture from multiple body fluids of infected or convalescent patients including blood, saliva, stool, vaginal fluid, sweat, and urine for days or months after illness. 36 Given the high volume of diarrhea and vomiting and the potential for fomite transmission, the frequency of environmental contamination and survival of Ebola virus is of high concern. Several studies have assessed the frequency of contamination within the health care 37,39 or RT-PCR.…”

Role of viral bioaerosols in nosocomial infections and measures for prevention and control

“…One study showed that a large community outbreak in SARS in Hong Kong could be explained by aerosol transmission (Yu et al, 2004), while another study showed that environmental surfaces in the hospitals could be contaminated with SARS-CoV and therefore contact transmission was considered possible (Dowell et al, 2004). It has been suggested that respiratory transmission of Ebola viruses could occur, although this is controversial (Osterholm et al, 2015;Vetter et al, 2016). Several experimental studies indicate that EBOV can be transmitted through aerosols in various animal species (Jaax et al, 1995;Weingartl et al, 2012).…”