A woman in Liberia contracted Ebola after having sexual intercourse with a male survivor of the disease who had been declared Ebola negative:

A woman in Liberia contracted Ebola after having sexual intercourse with a male survivor of the disease who had been declared Ebola negative

Ebola RNA Persistence in Semen of Ebola Virus Disease Survivors — Preliminary Report

New England Journal of Medicine, October 14, 2015

Gibrilla F. Deen, M.D., Barbara Knust, D.V.M., Nathalie Broutet, M.D., Ph.D., Foday R. Sesay, M.D., Pierre Formenty, D.V.M., Christine Ross, M.D., Anna E. Thorson, M.D., Ph.D., Thomas A. Massaquoi, M.D., Jaclyn E. Marrinan, M.Sc., Elizabeth Ervin, M.P.H., Amara Jambai, M.D., Suzanna L.R. McDonald, Ph.D., Kyle Bernstein, Ph.D., Alie H. Wurie, M.D., Marion S. Dumbuya, R.N., Neetu Abad, Ph.D., Baimba Idriss, M.D., Teodora Wi, Ph.D., Sarah D. Bennett, M.D., Tina Davies, M.S., Faiqa K. Ebrahim, M.D., Elissa Meites, M.D., Dhamari Naidoo, Ph.D., Samuel Smith, M.D., Anshu Banerjee, Ph.D., Bobbie Rae Erickson, M.P.H., Aaron Brault, Ph.D., Kara N. Durski, M.P.H., Jorn Winter, Ph.D., Tara Sealy, M.P.H., Stuart T. Nichol, Ph.D., Margaret Lamunu, M.D., Ute Ströher, Ph.D., Oliver Morgan, Ph.D., and Foday Sahr, M.D.

DOI: 10.1056/NEJMoa1511410

The number of new cases of Ebola virus disease (EVD) in western Africa has declined from a peak of 1063 cases in the week of October 9, 2014, to fewer than 10 confirmed cases per week for 11 consecutive weeks as of October 7, 2015.1. The main mode of transmission is direct contact with the blood or body fluids of a person with EVD or from the body of a person who died from EVD.2,3However, Ebola virus can persist in the body fluids of survivors during convalescence,4,5 which may result in transmission of the virus. The potential for the persistence of Ebola virus in the semen of male survivors raises concern regarding the possible transmission of the virus to sexual partners.6

Previously, survivors of EVD were told to practice sexual abstinence or to use a condom for 3 months after recovery. These recommendations were based on virus-isolation results from semen specimens obtained from eight survivors of EVD or Marburg virus disease in previous epidemics,5,7-10 in which the longest period that infectious virus was found in semen after the onset of symptoms was 82 days.

In March 2015, a woman in Liberia received a diagnosis of EVD and her only potential exposure that could be ascertained was sexual contact with a male survivor of EVD. Further investigation found Ebola virus RNA in the survivor’s semen 199 days after the onset of his symptoms, with a genetic sequence that matched the sequence from the case patient.11 Although no infectious virus was detected in this semen specimen, the possibility that infectious Ebola virus could persist in the semen of survivors approximately 6 months after the onset of illness prompted the World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) to revise their guidelines regarding the length of time that survivors of EVD should avoid unprotected sexual activity.12,13

There are thousands of survivors of EVD in western Africa, and many are sexually active men. Sexual transmission of the Ebola virus could possibly result in new outbreaks several weeks or months after all known chains of transmission in the region have stopped. Although the epidemiologic observations to date suggest that sexual transmission is a rare event, the Sierra Leone Ministry of Health and Sanitation, in collaboration with the Sierra Leone Ministry of Defense, the Sierra Leone Ministry of Social Welfare, Gender, and Children’s Affairs, the WHO, and the CDC initiated a study of the duration of virus persistence in the body fluids of survivors in Sierra Leone. We report initial findings from the pilot phase of the study, which investigated the persistence and viability of Ebola virus in the semen of male survivors of EVD.



We gathered evidence showing that an Ebola virus RNA signal on quantitative RT-PCR was found in the semen of male survivors of EVD at least 9 months after the onset of symptoms. Because the data in this report are cross sectional, we are limited to reporting only the point prevalence among participants rather than describing individual-level persistence and clearance of the RT-PCR signal over time. Among this cross-sectional group of participants, all 9 male survivors who provided a sample during the first 3 months after the onset of illness had positive results on quantitative RT-PCR. During months 4 to 6, more than half the enrolled survivors had positive results on quantitative RT-PCR. The percentage of male survivors with positive results continued to decline over time, with approximately one quarter of the participants having positive findings on quantitative RT-PCR at 7 to 9 months after onset.

We observed that the median cycle-threshold values for the NP and VP40 gene targets increased over time, which indicated that the median quantity of viral RNA in the semen decreased over time. Our study cohort included only survivors whose onset of illness was 10 months or less before enrollment, so we do not yet know how long survivors of EVD may have Ebola RNA detectable on quantitative RT-PCR in semen. Follow-up of this cohort is ongoing, and this report will be finalized when additional data to address the issues of infectivity are available.

The detection of Ebola virus RNA by quantitative RT-PCR does not necessarily indicate that infectious virus is present. The quantitative RT-PCR assay used in this study is highly sensitive, with a detection limit per reaction of 30 median tissue-culture–infective doses (TCID50) for the NP and VP40 gene targets in blood and urine samples to which a known quantity of live virus was added.14,15 However, the targeted RNA sequences detected by quantitative RT-PCR could be detecting the presence of the full genome from an intact replicating virus or from smaller fragments that are unable to replicate and infect a host cell. Virus-isolation assays are under way, in which the specimens will be inoculated onto mammalian cells and the cell cultures will be observed for cytopathic effect as the virus replicates, which is the best available standard to approximate infectivity.

The cycle-threshold value for Ebola RNA has been shown to be a good approximation of the viral load in blood,16 with an increasing cycle-threshold value indicating a decrease in the viral load. A limited study that examined the relationship between cycle-threshold values and virus isolation did not detect infectious virus in blood specimens from patients with EVD when cycle-threshold values were greater than 35.5 with the NP gene target.17 However, experiments have not yet been performed to predict the cycle-threshold value at which viable virus can no longer be cultured in semen. It is possible that even if men provide samples that are positive on quantitative RT-PCR several months after the onset of illness, the higher cycle-threshold values (such as the median values of 37.0 value with the NP gene target and 35.6 with the VP40 gene target at 7 to 9 months observed in the current study) may indicate that their semen is no longer infectious. Ongoing serial testing until the men in this study cohort have two consecutive negative results on quantitative RT-PCR, as defined above, and performing viral culture of the RT-PCR–positive specimens will enable us to address the question of the duration of persistence of potentially infectious virus in semen.

Our cross-sectional analysis of baseline data describes the preliminary results in this cohort. Follow-up of this preliminary report continues so that we may investigate the presence and persistence of virus in the semen of survivors of EVD, including studying the relationship among cycle-threshold values, viral isolation, and genome sequencing; assessing how long semen from a survivor of EVD will remain positive; and exploring risk factors for the persistence of Ebola virus in semen.

Although our findings are based on a cohort of 100 male survivors of EVD, the public health implications are still uncertain. The ongoing study of quantitative RT-PCR positivity and virus isolation in semen will provide better estimates of the duration of viral persistence and related probabilities of persistence at various points in time.

We do not yet have sufficient information to assess the risk of transmission through sexual intercourse, oral sex, or other sex acts from men with viable virus in their semen. Before the Ebola epidemic in western Africa, a single case of Marburg virus disease and one case of EVD had been linked to sexual contact with survivors of Marburg virus disease and EVD, respectively.7,10 In western Africa, cases that have been linked to sexual contact with survivors of EVD have not been systematically documented, and fewer than 20 in total have been suspected (Knust B, CDC; Formenty P, WHO: personal communication).

Although the potential contribution of sexual transmission to the scale of the epidemic is largely unknown, the unprecedented number of more than 16,000 survivors of EVD across Sierra Leone, Guinea, and Liberia, roughly half of whom are male, creates the potential for transmission and initiation of new chains of transmission, even months after the outbreak has ended. Even though there have been only rare cases of EVD linked to sexual transmission, research is needed to investigate whether infectious virus may be present in vaginal fluid or other body fluids after recovery, and the testing of additional body fluids in both male and female survivors is planned.

Programs such as semen testing and preventive behavioral counseling are needed in order to help survivors of EVD appreciate and mitigate the possible risk of sexual transmission. Such programs would help men and women understand their individual risk and take appropriate measures to protect their sexual partners, specifically in regard to condom use and disposal, and could provide links to care and counseling programs for survivors. Because semen-testing programs are not yet universally available, outreach activities are needed to provide education regarding recommendations and risks to survivor communities and sexual partners of survivors in a way that does not further stigmatize the community of survivors of EVD.

Persons who survive EVD face myriad challenges. Many survivors have family members and friends who died from EVD. Many are unemployed, face stigma from their communities, and have lingering sequelae in addition to the risk of persisting virus in semen. Due respect and continuing efforts that have strong sustainable support from within the local communities are crucial in mitigating negative effects in terms of further stigma attached to survivors.

Supported by the WHO, the CDC, the Sierra Leone Ministry of Health and Sanitation, and the Joint United Nations Program on HIV/AIDS (UNAIDS).


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