Persistence of Ebola virus in the semen of male survivors

Persistence of Ebola virus in the semen of male survivors

Roland K. Hartmann1, Arnold Grünweller1, Thomas Strecker2

1Institute of Pharmaceutical Chemistry, Philipps-University Marburg, Marburg, Germany; 2Institute of Virology, Philipps-University Marburg, Marburg, Germany

Correspondence to: Roland K. Hartmann. Institute of Pharmaceutical Chemistry, Philipps-University Marburg, Marbacher Weg 6, 35037 Marburg, Germany. Email:

Provenance: This is a Guest Editorial commissioned by the Editor-in-Chief: Baoli Zhu (Jiangsu Province Center for Disease Control and Prevention, Nanjing, China).

Comment on: Soka MJ, Choi MJ, Baller A, et al. Prevention of sexual transmission of Ebola in Liberia through a national semen testing and counselling programme for survivors: an analysis of Ebola virus RNA results and behavioural data. Lancet Glob Health 2016;4:e736-43.

Received: 25 November 2016; Accepted: 30 November 2016; Published: 17 January 2017.

doi: 10.21037/jphe.2016.12.16


The 2014–2016 epidemic of Ebola virus (EBOV) in West Africa was the longest and geographically most widespread Ebola outbreak ever recorded. According to the World Health Organization, it caused more than 28,616 human cases and 11,310 fatalities, but the actual case numbers are assumed to be even higher due to undetected and unreported cases. The unprecedented dimension of the outbreak has resulted in thousands of survivors of Ebola virus disease (EVD), many of whom suffer from physical and mental health problems (1-3). In addition, there is evidence that EBOV can persist for an extended period of time during the convalescent phase in specific body compartments of EVD survivors, including the central nervous system, eyes, amniotic fluid, placenta, breast milk and seminal fluid (4-11). Transmission of EBOV during convalescence may potentially lead to reinfections within families and local communities where the virus had seemingly been eradicated before. Given the large number of male EVD survivors in West Africa, particularly the presence of EBOV in semen raised concerns of EBOV transmission through sexual intercourse.

At present, only limited data is available for how long viable EBOV particles naturally persist in the seminal and other body fluids of EVD survivors. Such information is important to understand the mechanism of EBOV persistence and its shedding in various body fluids, including semen, in order to estimate and mitigate the risk of transmission from EVD survivors. Studies from previous EBOV outbreaks have shown that infectious EBOV can be isolated from the semen of survivors up to 82 days after onset of disease symptoms (9). Data from the recent West African outbreak even demonstrated the presence of EBOV genetic material (RNA) in the semen of survivors for up to 9 months after disease onset, with individual reports showing viral RNA persistence for more than 1.5 years (6,12,13). Detection of EBOV nucleic acid, however, may only reflect the presence of residual viral RNA and therefore does not provide information about the presence of viable, infectious virions as well as the contagiousness of body fluids from survivors. Although in most studies the relationship between prolonged detection of viral RNA in semen and virus infectivity based on cell culture or animal models has yet to be determined, documented cases of sexual transmission of EBOV in Liberia and Guinea up to 470 days after onset of illness indicate that transmissible infectious virus can persist in the seminal fluid for a longer time than previously recognized (12,14). While available epidemiological information indicates that sexual transmission is rather rare, sexual partners of male survivors can be at risk of contracting EVD due to virus persistence and seminal shedding of EBOV. This highlights the need for continued post-outbreak surveillance and preventive measure activities aiming at reducing the potential risk of sexual transmission of persisting EBOV.

Liberia’s Men’s Health Screening Program (MHSP)

A very recent publication by Soka et al. in the “The Lancet Global Health” (15) reports on experiences and findings that were gained in the context of Liberia’s Men’s Health Screening Program (MHSP), the first and ongoing national semen testing program for EBOV survivors operated at three hospitals. Males ≥15 years with an Ebola hospital discharge certificate were eligible for the program which includes semen sample testing for EBOV RNA (sequences specific for the first and third gene, NP and VP40) as well as counseling on safe sexual practices. After two consecutive negative semen tests, participants are released from the program. Information on sociodemographics and sexual behaviour was gathered at all appointments. For 38 of the 429 participants, EBOV RNA was detectable in at least one semen specimen, of which 24 had recovered from the disease at least 1 year ago and 1.5 years as the longest interval. Men aged >40 years had a higher incidence of their semen sample tested positive. Many participants, who declared no condom use at enrolment or stated that they were sexually active, reported using condoms or being abstinent at their first follow-up visit. Thus, the program makes EBOV survivors successfully aware of their individual risk and motivates them to protect their sexual partners.

Liberia’s MHSP again conclusively illustrates the importance of aftercare (post-outbreak surveillance) programs for epidemic diseases, which combine body fluid testing with inquiries and counseling on relevant social and behavioral aspects. Such programs should be firmly installed not only for EBOV but also for HIV, Zika, Dengue or Lassa infections. An important issue is an appropriate financial incentive for program participants, considering that such infections primarily hit poorer countries, and often participants have to master long and troublesome access routes to get to their screening unit. Also, mobile counselors that visit participants in their secluded home villages should be an important component of such programs to foster the compliance of participants.

Infectivity of viral RNA detected in body fluids

As already mentioned, a key question is whether viral RNA detected in semen samples represents infectious viral particles or non-infectious genomic fragments. Here, testing of aftercare semen samples in sensitive cell culture systems or animal models should be informative to answer this question. Also, future research efforts have to be dedicated to exploring the mechanistic basis of how EBOV succeed to survive in immune privileged organs, including the testis, for extended periods. Exosomes may play a role in these processes, as detailed below.

Exosomes and viral infections

Many different viruses use exosomes as a kind of Trojan horse which protects them from host immune responses, thus increasing their persistence [for review see (16)]. Furthermore, exosomes have been identified as vehicles for virus transmission, a strategy that may broaden the number of cell types which can be infected. Exosomal vesicles, which originate from multivesicular bodies (MVBs) and can be released from nearly all types of cells, play an important role in various biological processes such as intercellular communication as well as immune regulation and signaling. They can be isolated from various body fluids including saliva, plasma, serum, breast milk, seminal fluid and bronchial alveolar lavage. Exosomes can cross biological barriers such as the blood-brain, blood-ocular or blood-testis barrier, thus enabling viral access to immune-privileged tissues and organs (16).

For hepatitis C virus (HCV), a member of the Flaviviridae, it was shown that its RNA genome can remain in endosome-derived intraluminal vesicles to maintain infectious particles which can be secreted via exosomes (17). Indeed, exosomes isolated from sera of chronic HCV-infected patients contained replication-competent HCV RNA genomes (18). Moreover, it could be shown that exosome-mediated transmission of HCV can establish a productive infection (19). The picornavirus hepatitis A virus seems to use a similar route for virus transmission, as the virus hijacks endosomal membranes for encapsulation and subsequent release; such enveloped, fully infectious viruses resemble exosomes (20). It was also shown that Bunyaviruses such as the Rift Valley fever virus (RVFV) or the SFTS (severe fever with thrombocytopenia syndrome) virus store both viral RNA and viral proteins in exosomes, and such exosomes are able to infect host cells via receptor-independent transmission (21,22). Very recently, it has been shown that the Ebola matrix protein VP40 is packaged into exosomes that are taken up by T- and myeloid immune cells; in such recipient cells, VP40 is able to induce apoptosis and to downregulate the RNAi machinery, thereby weakening the host's adaptive immune system and its defense against the viral infection (23).

At present, our understanding how EBOV maintains viral reservoirs is only fragmentary. The isolation of EBOV RNA from immune-privileged sites several hundred days after recovery from infection is disturbing and needs to be analyzed in much more detail to understand how EBOV persists and is able to spread its infectious components over such long time periods. Thus, research on cell and tissue tropism in immune-privileged organs as well as the possible role of exosomes in EBOV infection is an urgent requirement towards a better mechanistic understanding of EBOV persistence and virus transmission long after recovery from acute illness.

Concluding remarks

Despite open scientific questions, Liberia’s MHSP is a paradigm for a successful post-outbreak surveillance program that combines body fluid testing with inquiries and counseling on relevant social and behavioral aspects. The installation and permanent maintenance of comparable programs is strongly recommended not only for EBOV but also for other sexually transmissible viral pathogens with great public health impact.


We thank Hans-Dieter Klenk for critical reading of the manuscript.

Funding: Research of the authors was funded by the German Research Council [SFB 1021 TP A02 (RK Hartmann) and TP B05 (T Strecker)], the LOEWE Research Cluster “Medical RNomics” (RK Hartmann and A Grünweller) and the Universitätsklinikum Gießen und Marburg (Project No. 27/2016 MR to T Strecker).


Conflicts of Interest: The authors have no conflicts of interest to declare.


  1. Mattia JG, Vandy MJ, Chang JC, et al. Early clinical sequelae of Ebola virus disease in Sierra Leone: a cross-sectional study. Lancet Infect Dis 2016;16:331-8. [Crossref] [PubMed]
  2. Rabelo I, Lee V, Fallah MP, et al. Psychological Distress among Ebola Survivors Discharged from an Ebola Treatment Unit in Monrovia, Liberia - A Qualitative Study. Front Public Health 2016;4:142. [Crossref] [PubMed]
  3. Tiffany A, Vetter P, Mattia J, et al. Ebola Virus Disease Complications as Experienced by Survivors in Sierra Leone. Clin Infect Dis 2016;62:1360-6. [Crossref] [PubMed]
  4. Bausch DG, Towner JS, Dowell SF, et al. Assessment of the risk of Ebola virus transmission from bodily fluids and fomites. J Infect Dis 2007;196 Suppl 2:S142-7. [Crossref] [PubMed]
  5. Caluwaerts S, Fautsch T, Lagrou D, et al. Dilemmas in Managing Pregnant Women With Ebola: 2 Case Reports. Clin Infect Dis 2016;62:903-5. [Crossref] [PubMed]
  6. Deen GF, Knust B, Broutet N, et al. Ebola RNA Persistence in Semen of Ebola Virus Disease Survivors - Preliminary Report. N Engl J Med 2015. [Epub ahead of print]. [Crossref] [PubMed]
  7. Jacobs M, Rodger A, Bell DJ, et al. Late Ebola virus relapse causing meningoencephalitis: a case report. Lancet 2016;388:498-503. [Crossref] [PubMed]
  8. Moreau M, Spencer C, Gozalbes JG, et al. Lactating mothers infected with Ebola virus: EBOV RT-PCR of blood only may be insufficient. Euro Surveill 2015;20:21017. [Crossref] [PubMed]
  9. Rodriguez LL, De Roo A, Guimard Y, et al. Persistence and genetic stability of Ebola virus during the outbreak in Kikwit, Democratic Republic of the Congo, 1995. J Infect Dis 1999;179 Suppl 1:S170-6. [Crossref] [PubMed]
  10. Sagui E, Janvier F, Baize S, et al. Severe Ebola Virus Infection With Encephalopathy: Evidence for Direct Virus Involvement. Clin Infect Dis 2015;61:1627-8. [Crossref] [PubMed]
  11. Varkey JB, Shantha JG, Crozier I, et al. Persistence of Ebola Virus in Ocular Fluid during Convalescence. N Engl J Med 2015;372:2423-7. [Crossref] [PubMed]
  12. Diallo B, Sissoko D, Loman NJ, et al. Resurgence of Ebola Virus Disease in Guinea Linked to a Survivor With Virus Persistence in Seminal Fluid for More Than 500 Days. Clin Infect Dis 2016;63:1353-6. [Crossref] [PubMed]
  13. Sow MS, Etard JF, Baize S, et al. New Evidence of Long-lasting Persistence of Ebola Virus Genetic Material in Semen of Survivors. J Infect Dis 2016;214:1475-6. [Crossref] [PubMed]
  14. Mate SE, Kugelman JR, Nyenswah TG, et al. Molecular Evidence of Sexual Transmission of Ebola Virus. N Engl J Med 2015;373:2448-54. [Crossref] [PubMed]
  15. Soka MJ, Choi MJ, Baller A, et al. Prevention of sexual transmission of Ebola in Liberia through a national semen testing and counselling programme for survivors: an analysis of Ebola virus RNA results and behavioural data. Lancet Glob Health 2016;4:e736-43. [Crossref] [PubMed]
  16. Anderson MR, Kashanchi F, Jacobson S. Exosomes in Viral Disease. Neurotherapeutics 2016;13:535-46. [Crossref] [PubMed]
  17. Longatti A, Boyd B, Chisari FV. Virion-independent transfer of replication-competent hepatitis C virus RNA between permissive cells. J Virol 2015;89:2956-61. [Crossref] [PubMed]
  18. Bukong TN, Momen-Heravi F, Kodys K, et al. Exosomes from hepatitis C infected patients transmit HCV infection and contain replication competent viral RNA in complex with Ago2-miR122-HSP90. PLoS Pathog 2014;10:e1004424. [Crossref] [PubMed]
  19. Ramakrishnaiah V, Thumann C, Fofana I, et al. Exosome-mediated transmission of hepatitis C virus between human hepatoma Huh7.5 cells. Proc Natl Acad Sci U S A 2013;110:13109-13. [Crossref] [PubMed]
  20. Feng Z, Hensley L, McKnight KL, et al. A pathogenic picornavirus acquires an envelope by hijacking cellular membranes. Nature 2013;496:367-71. [Crossref] [PubMed]
  21. Silvas JA, Popov VL, Paulucci-Holthauzen A, et al. Extracellular Vesicles Mediate Receptor-Independent Transmission of Novel Tick-Borne Bunyavirus. J Virol 2015;90:873-86. [Crossref] [PubMed]
  22. Ahsan NA, Sampey GC, Lepene B, et al. Presence of Viral RNA and Proteins in Exosomes from Cellular Clones Resistant to Rift Valley Fever Virus Infection. Front Microbiol 2016;7:139. [Crossref] [PubMed]
  23. Pleet ML, Mathiesen A, DeMarino C, et al. Ebola VP40 in Exosomes Can Cause Immune Cell Dysfunction. Front Microbiol 2016;7:1765. [Crossref] [PubMed]
doi: 10.21037/jphe.2016.12.16
Cite this article as: Hartmann RK, Grünweller A, Strecker T. Persistence of Ebola virus in the semen of male survivors. J Public Health Emerg 2017;1:23.