Ebola Virus Disease Survivors Research Articles

Ebola Virus-Specific Neutralizing Antibody Persists at High Levels in Survivors 2 Years After Resolution of Disease in a Sierra Leonean Cohort.

Ebola virus (EBOV) infection results in Ebola virus disease (EVD), an often severe disease with a nonspecific presentation. Since its recognition, periodic outbreaks of EVD continue to occur in sub-Saharan Africa. The 2013-2016 West African EVD outbreak was the largest recorded, resulting in a substantial cohort of EVD survivors with persistent health complaints and variable immune responses. In this study, we characterize humoral immune responses in EVD survivors and their contacts in Eastern Sierra Leone. We found high levels of EBOV IgG in EVD survivors and lower yet substantial antibody levels in household contacts, suggesting subclinical transmission. Neutralizing antibody function was prevalent but variable in EVD survivors, raising questions about the durability of immune responses from natural infection with EBOV. Additionally, we found that certain discrete symptoms-ophthalmologic and auditory-are associated with EBOV IgG seropositivity, while an array of symptoms are associated with the presence of neutralizing antibody.

The state of mental health among Ebola virus disease survivors through a cross-sectional study in Sierra Leone

BackgroundThe West African Ebola virus disease (EVD) epidemic resulted in >28 000 disease cases and >11 000 fatalities. The unprecedented number of survivors from this epidemic has raised questions about...

Ebola virus disease sequelae and viral persistence in animal models: Implications for the future.

Ebola virus disease (EVD), caused by infection with Ebola virus, results in severe, acute illness with a high mortality rate. As the incidence of outbreaks of EVD increases and with the development and approval of medical countermeasures (MCMs) against the acute disease, late phases of EVD, including sequelae, recrudescence, and viral persistence, are occuring more frequently and are now a focus of ongoing research. Existing animal disease models recapitulate acute EVD but are not suitable to investigate the mechanisms of these late disease phenomena. Although there are challenges in establishing such a late disease model, the filovirus research community has begun to call for the development of an EBOV persistence model to address late disease concerns. Ultimately, this will aid the development of MCMs against late disease and benefit survivors of future EVD and filovirus outbreaks.

351 - Understanding drivers of post-Ebola syndrome (PES) in pediatric survivors of Ebolavirus disease: characterization and the way forward

351 - Understanding drivers of post-Ebola syndrome (PES) in pediatric survivors of Ebolavirus disease: characterization and the way forward

Perceptions toward Ebola vaccination and correlates of vaccine uptake among high-risk community members in North Kivu, Democratic Republic of the Congo.

The tenth Ebola Virus Disease (EVD) outbreak (2018-2020, North Kivu, Ituri, South Kivu) in the Democratic Republic of the Congo (DRC) was the second-largest EVD outbreak in history. During this outbreak, Ebola vaccination was an integral part of the EVD response. We evaluated community perceptions toward Ebola vaccination and identified correlates of Ebola vaccine uptake among high-risk community members in North Kivu, DRC. In March 2021, a cross-sectional survey among adults was implemented in three health zones. We employed a sampling approach mimicking ring vaccination, targeting EVD survivors, their household members, and their neighbors. Outbreak experiences and perceptions toward the Ebola vaccine were assessed, and modified Poisson regression was used to identify correlates of Ebola vaccine uptake among those offered vaccination. Among the 631 individuals surveyed, most (90.2%) reported a high perceived risk of EVD and 71.6% believed that the vaccine could reduce EVD severity; however, 63.7% believed the vaccine had serious side effects. Among the 474 individuals who had been offered vaccination, 397 (83.8%) received the vaccine, 180 (45.3%) of those vaccinated received the vaccine after two or more offers. Correlates positively associated with vaccine uptake included having heard positive information about the vaccine (RR 1.30, 95% CI 1.06-1.60), the belief that the vaccine could prevent EVD (RR 1.23, 95% CI 1.09-1.39), and reporting that religion influenced all decisions (RR 1.13, 95% CI 1.02-1.25). Ebola vaccine uptake was high in this population, although mixed attitudes and vaccine delays were common. Communicating positive vaccine information, emphasizing the efficacy of the Ebola vaccine, and engaging religious leaders to promote vaccination may aid in increasing Ebola vaccine uptake during future outbreaks.

Understanding knowledge, attitudes and practices on Ebola Virus Disease: a multi-site mixed methods survey on preparedness in Rwanda

BackgroundThe overall goal of this survey was to understand the knowledge, attitudes, and practices related to the Ebola Virus Disease (EVD) in Rwanda.MethodsThis mixed-method cross-sectional survey was conducted in five selected districts of Rwanda. Quantitative data were collected from 1,010 participants using Kobo Collect Software and the analysis was performed using SPSS and Python software. Qualitative data were specifically collected from 98 participants through Key Informant Interviews (KIIs) and Focus Group Discussion (FGDs). Interview transcripts were imported into NVIVO 8 for coding and subsequent analysis.ResultsAs per our quantitative findings, we report that from the 1,010 respondents, 99.6% reported having previously heard of Ebola, 97.2% believed that vaccination is important in combatting the disease and 93.3% of individuals reported a willingness to receive vaccination should one become available. Around 54% of the respondents were correct in identifying that the disease is of a viral origin which originates from wild animals (42.1%). When asked if they believed that Rwanda is at risk of an EVD outbreak, 90% of the respondents believe that the country is at risk of an EVD outbreak, and the cofactors *gender* and *whether people dwell in Rubavu/Rusizi* were found to significantly impact their perception of threat. As per our qualitative findings, the respondents mentioned that both geographical proximity and relations with the Democratic Republic of Congo place Rwanda at risk of developing an internal outbreak. Although the respondents seemed to be aware of the Ebola prevention behaviours, it was noted that some of them will require significant time before reintegrating into the community an EVD survivor, as they will first need assurance that the patient has fully recovered. Therefore, the qualitative findings reinforce what we originally reported in the quantitative approach to this study.ConclusionOur results show that there was high EVD-related knowledge and awareness among the general population in Rwanda. However, for strong public health awareness, preparedness, and protection, a massive investment should always be made in education about EVD with a special focus on districts neighboring countries where the disease is consistently being reported.

Effect of anti-Ebola virus monoclonal antibodies on endogenous antibody production in survivors of Ebola virus disease in the Democratic Republic of the Congo: an observational cohort study

The use of specific anti-Ebola virus therapy, especially monoclonal antibodies, has improved survival in patients with Ebola virus disease. We aimed to assess the effect of monoclonal antibodies on anti-Ebola virus antibody responses in survivors of the 2018-20 Ebola outbreak in the Democratic Republic of the Congo. In this observational prospective cohort study, participants were enrolled at three Ebola survivor clinics in Beni, Mangina, and Butembo (Democratic Republic of the Congo). Eligible children and adults notified as survivors of Ebola virus disease (ie, who had confirmed Ebola virus disease [RT-PCR positive in blood sample] and were subsequently declared recovered from the virus [RT-PCR negative in blood sample] with a certificate of recovery from Ebola virus disease issued by an Ebola treatment centre) during the 2018-20 Ebola virus disease outbreak were invited to participate in the study. Participants were recruited on discharge from Ebola treatment centres and followed up for 12-18 months depending on recruitment date. Routine follow-up assessments were done at 1, 3, 6, and 12-18 months after inclusion. We collected sociodemographic (age, sex, visit site), clinical (anti-Ebola virus drugs), and laboratory data (RT-PCR and Ct values). The primary outcome was the antibody concentrations against Ebola virus glycoprotein, nucleoprotein, and 40-kDa viral protein antigens over time assessed in all participants. Antibody concentrations were measured by the multiplex immunoassay, and the association between anti-Ebola virus antibody levels and the relevant exposures, such as anti-Ebola virus disease drugs (ansuvimab, REGN-EB3, ZMapp, or remdesivir), was assessed using both linear and logistic mixed regression models. This study is registered at ClinicalTrials.gov, NCT04409405. Between April 16, 2020, and Oct 18, 2021, 1168 survivors were invited to participate in the Les Vainqueurs d'Ebola cohort study. 787 survivors were included in the study, of whom 358 had data available for antibody responses. 85 (24%) of 358 were seronegative for at least two Ebola virus antigens on discharge from the Ebola treatment centre. The antibody response over time fluctuated but a continuous decrease in an overall linear evolution was observed. Quantitative modelling showed a decrease in nucleoprotein, glycoprotein, and VP-40 antibody concentrations over time (p<0·0001) with the fastest decrease observed for glycoprotein. The probability of being seropositive for at least two antigens after 36 months was 53·6% (95% CI 51·6-55·6) for participants who received ansuvimab, 73·5% (71·5-75·5) for participants who received REGN-EB3, 76·8% (74·8-78·8) for participants who received remdesivir, and 78·5% (76·5-80·5) for participants who received ZMapp. Almost a quarter of survivors were seronegative on discharge from the Ebola treatment centre and antibody concentrations decreased rapidly over time. These results indicate that monoclonal antibodies might negatively affect the production of anti-Ebola virus antibodies in survivors of Ebola virus disease which could increase the risk of reinfection or reactivation. The French National Agency for AIDS Research-Emergent Infectious Diseases-The French National Institute of Health and Medical Research, the French National Research Institute for Development, and the European and Developing Countries Clinical Trials Partnership. For the French translation of the abstract see Supplementary Materials section.

Preparedness for future outbreaks: strengthening surveillance of survivors of Ebola virus disease

Preparedness for future outbreaks: strengthening surveillance of survivors of Ebola virus disease

Beyond survival: unraveling the dynamics of Ebola virus resurgence in Sub-Saharan Africa and the remarkable journey of survivors

Ebola virus disease (EVD) remains a significant public health threat, with sporadic outbreaks occurring in Sub-Saharan Africa. Survivors of EVD may experience various post-infection symptoms, collectively known as post-Ebola virus syndrome (PES), which include chronic arthralgia, uveitis, headache, and psychosocial stressors. In this review, we discuss the persistence of Ebola virus in survivors and its possible role in the reemergence of current outbreaks. We highlight that waning immunity of survivors enhances viral persistence and may lead to viral reactivation and recurrence of disease in previously affected tissues. The delicate equilibrium between diminished immune cell surveillance and limited viral replication may lead to enduring chronic inflammation. Our systematic review, based on an extensive survivor cohort, underscores the importance of continued research and preparedness efforts to combat future outbreaks through adequate surveillance and timely public health interventions. This review serves as a comprehensive guide to understanding the complexities of EVD survivorship, the challenges of PES, and the strategies to mitigate its impact.

Stigmatization of Ebola virus disease survivors in 2022: A cross-sectional study of survivors in Sierra Leone

BackgroundEvidence has demonstrated a high proportion of Ebola virus disease (EVD) survivors experienced stigma due to the disease. This study sought to understand the longer-term effects of stigma encountered by survivors of the 2014–2016 EVD epidemic living in Sierra Leone. MethodsThis was a cross-sectional study of 595 EVD survivors and 403 close contacts (n = 998) from Sierra Leone. Assessments were conducted using a three-part survey between November 2021 to March 2022. We explored the socio-demographic factors associated with stigma experienced by EVD survivors. Findings50·6 % (n = 301) of EVD survivors reported that they continued to experience at least one aspect of stigma. Females were disproportionately affected by stigma, with 45·2 % of females reporting isolation from friends and family compared to 33·9 % of men (p = 0·005). Multivariable logistic regression models revealed those aged 40–44, living rurally, and reporting an acute infection longer than seven days was associated with EVD-related stigma at the time of survey. InterpretationThis study demonstrates stigma is still prevalent among people who survived EVD in 2022. It also identified socio-demographic factors associated with stigma that can be used for targeting interventions. Importantly, this highlights the continued need for EVD survivors to access mental healthcare and social support systems well after disease recovery. FundingThis study was funded by the Canadian Institutes for Health Research (Grant no. PJT-175098. JK is funded by a Tier 2 Canada Research Chair in the Molecular Pathogenesis of Emerging and Re-Emerging Viruses. SS is funded by a Tier 2 Canada Research Chair in Program Science and Global Public Health.

Prevalence and Factors Related to Post-traumatic Stress Disorder and Depression Symptoms Among Children and Adolescents Survivors and Orphans of Ebola Virus Disease in Democratic Republic of the Congo Eastern Regions During the COVID-19 Pandemic

PurposeAlthough previous studies have shown a high prevalence of mental health problems among adult Ebola virus disease survivors, no studies have yet been conducted on mental health problems among children and adolescents in affected regions. Consequently, the current study aimed to examine the prevalence and factors associated with depression and post-traumatic stress disorder (PTSD) among children and adolescent survivors and orphans by utilizing a cross-sectional survey following the 2018–2020 epidemic in Eastern Democratic Republic of the Congo. MethodsA total of 146 survivors (mean age = 13.62, standard deviation [SD] = 2.50, 49.32% female), 233 orphans (mean age = 13.18, SD = 2.96, 53.32% female), and 34 orphan-survivor participants (mean age = 13.39, SD = 2.87, 44.12% female) were recruited. Participants completed measures assessing depression and PTSD symptoms, traumatic experiences, and stigma related to Ebola and COVID-19. ResultsThe prevalence of depression and PTSD symptoms was 87.32% and 44.42%, respectively. Results showed significant differences in depression and PTSD symptoms between orphan-survivors (100% and 97.06%), survivors (90.21% and 75.86%), and orphans (83.48% and 16.52%; χ2(2) = 9.02; p = .011 and χ2(2) = 168.85; p < .001). Experience of traumatic events, Ebola stigmatization, and COVID-19 stigmatization positively predicted depression and PTSD symptoms. The regression models explained 61%–72% of the variance of depression and PTSD. DiscussionThe results reveal that the Ebola virus disease and its associated grief severely jeopardize the mental health of children and adolescents in affected regions. Despite the relative paucity of resources, intervention programs may be helpful to minimize associated stigma and promote psychological support.

Visual acuity and vision-related quality of life outcomes following cataract surgery in Ebola virus disease survivors.

The objectives of this study were to assess relationships between vision-related quality of life (QoL) and visual acuity (VA) in Ebola virus disease (EVD) survivors after cataract surgery in the Ebola Viral Persistence in Ocular Tissues and Fluids (EVICT) Study. EVD survivors with undetectable Ebola virus (EBOV) ribonucleic acid in their aqueous humour were eligible to receive manual small-incision cataract surgery (MSICS). Among those that received surgery, assessments of VA and vision-related QoL were assessed pre-and post-cataract surgery. VA was converted from units on a tumbling 'E' chart to the logarithm of the minimal angle of resolution VA (logMAR VA). Vision-related QoL was assessed using the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25). Linear regression was used to evaluate the associations between VA and vision-related QoL. P = 0.05 was considered statistically significant for all analyses. Thirty-four EVD survivors underwent cataract surgery in the EVICT study. Before MSICS, the mean logMAR VA was 2.24 (standard deviation [SD]: 0.98), and the mean NEI-VFQ-25 composite score was 54 (SD: 15); however, there was no significant association between the pre-surgery measurements (average difference in VA/10 unit increase in NEI-VFQ-25: -0.04, 95% confidence interval (CI): -0.33-0.26, P = 0.80). There was a significant improvement in logMAR VA after MSICS (mean: 1.6, P < 0.001), but there was no significant change in the NEI-VFQ-25 composite (-0.87, 95% (CI): -10.32-8.59, P = 0.85). None of the subscales showed significant improvements (P > 0.12 for all); however, the magnitude of the mean change for distance activities (6.65), near activities (6.76), general vision (-7.69), social functioning (-9.13) and colour vision (13.33) met the criteria for a clinically meaningful difference (4-6). In the subset with paired measurements (n = 16), there were no significant association changes in logMAR VA and NEI VFQ-25 composite scores (P > 0.12 for all). Following cataract surgery, VA in EVD survivors improved, but these improvements were not reflected in NEI VFQ-25 composite scores or specific subscales; however, the small sample size limits generalizability absent more research. Differences in sociocultural context and activities that affect the QoL in resource-limited areas may contribute to the limitations seen with NEI VFQ-25. In addition, better eye dominance could contribute to any lack of association as NEI VFQ-25 evaluates vision as a whole. Further, assessment of factors contributing to improved QoL may help to define the impact of vision health in varied environments.

Pregnancy in people who have survived Ebola virus disease

Pregnancy in people who have survived Ebola virus disease

Long-Term Decrease in Intraocular Pressure in Survivors of Ebola Virus Disease in the Partnership for Research on Vaccines and Infectious Diseases in Liberia (PREVAIL) III Study.

Survivors of Ebola virus disease (EVD) experience decreased intraocular pressure (IOP) relative to unaffected close contacts during the first year of convalescence. Whether this effect persists over time and its relationship to intraocular pathology are unclear. We sought to determine whether IOP remained lower in survivors of EVD over 4 years of follow-up and to identify associated risk factors. Partnership for Research on Vaccines and Infectious Diseases in Liberia (PREVAIL) III is a 5-year, longitudinal cohort study of survivors of EVD and their close contacts and is a collaboration between the Liberian Ministry of Health and the United States National Institutes of Health. Participants who enrolled in PREVAIL III at John F. Kennedy Medical Center in Liberia, West Africa from June 2015 to March 2016 who underwent comprehensive ophthalmic evaluation annually for 5 consecutive visits. Intraocular pressure was measured at each visit by a handheld rebound tonometer using sterile tips. Comparisons are made between antibody-positive survivors and antibody-negative close contacts. Intraocular pressure, measured in mmHg, at each study visit. Of 565 antibody-positive survivors and 644 antibody-negative close contacts enrolled in the study at baseline, the majority of participants returned annually, with 383 (67.8%) and 407 (63.2%) participants, respectively, presenting for the final study visit at a median of 60 months after symptom onset. A sustained, relative decrease in IOP was observed in survivors relative to close contacts, with mean difference of-0.72 mmHg (95% confidence interval [CI]-1.18 to-0.27) at the final study visit. This difference remained constant throughout the study period (P= 0.4 for interaction over time). Among survivors, physical examination findings of vitreous cell and OCT findings of vitreous opacities both demonstrated a significant association with decreasedIOP at baseline (P < 0.05 for both). After adjusting for such factors, the difference throughout the follow-up (-0.93 mmHg, 95% CI,-1.23 to-0.63) remained significant. Survivors of EVD experienced a sustained decrease in IOP relative to close contacts over a 5-year period after EVD. The results highlight the importance of considering long-term sequelae of emerging infectious diseases within a population. Proprietary or commercial disclosure may be found after the references.

Survivors of Ebola virus disease exhibit elevated levels of autoantibodies

Abstract Survivors of Ebola virus disease (EVD) report a wide range of symptoms following recovery from acute viral infection, but underlying mechanisms are unclear. Many of these symptoms, collectively termed Post-Ebola Syndrome (PES), occur in the absence of detectable virus and resemble symptoms associated with autoimmune disease, such as arthralgia and myalgia, suggesting that EVD survivors may be experiencing a virus-induced autoimmune response. Studies in mice have shown that mice develop autoantibodies (autoAb) against HSP-60 and double stranded (ds) DNA that can bind to host tissues following Ebola virus (EBOV) infection. To determine if human EVD survivors also develop autoAb that may be associated with PES development, we profiled the humoral immune response of 354 survivors and 195 household contacts (HHC) from the 2014–2016 outbreak in Sierra Leone. Using Systems Serology, we measured the levels of antibodies against common autoantigens and found that EVD survivors had elevated levels of autoAb against dsDNA, HSP-60, IFNα, and citrullinated histone compared to HHC. As a subset of HHC were seropositive for EBOV glycoprotein (GP)-specific antibodies, separation of HHC into GP-seropositive and seronegative groups showed that the levels of autoAb in GP-seropositive HHC were elevated compared to GP-seronegative HHC, strongly suggesting that exposure/infection to EBOV tracks with presence of autoAb. As antibodies can activate innate immune cells via the antibody Fc domain, current studies are focused on analyzing the innate effector response mediated by these autoAb in EVD survivors and seropositive HHC. Together, our study highlights the potential role of autoAb in long-term sequelae associated with survival from EVD.

Ebola virus disrupts the inner blood-retinal barrier by induction of vascular endothelial growth factor in pericytes.

Ebola virus (EBOV) causes severe hemorrhagic fever in humans with high mortality. In Ebola virus disease (EVD) survivors, EBOV persistence in the eyes may break through the inner blood-retinal barrier (iBRB), leading to ocular complications and EVD recurrence. However, the mechanism by which EBOV affects the iBRB remains unclear. Here, we used the in vitro iBRB model to simulate EBOV in retinal tissue and found that Ebola virus-like particles (EBO-VLPs) could disrupt the iBRB. Cytokine screening revealed that EBO-VLPs stimulate pericytes to secrete vascular endothelial growth factor (VEGF) to cause iBRB breakdown. VEGF downregulates claudin-1 to disrupt the iBRB. Ebola glycoprotein is crucial for VEGF stimulation and iBRB breakdown. Furthermore, EBO-VLPs caused iBRB breakdown by stimulating VEGF in rats. This study provides a mechanistic insight into that EBOV disrupts the iBRB, which will assist in developing new strategies to treat EBOV persistence in EVD survivors.

Persistent intraocular Ebola virus RNA is associated with severe uveitis in a convalescent rhesus monkey

Despite increasing evidence that uveitis is common and consequential in survivors of Ebola virus disease (EVD), the host-pathogen determinants of the clinical phenotype are undefined, including the pathogenetic role of persistent viral antigen, ocular tissue-specific immune responses, and histopathologic characterization. Absent sampling of human intraocular fluids and tissues, these questions might be investigated in animal models of disease; however, challenges intrinsic to the nonhuman primate model and the animal biosafety level 4 setting have historically limited inquiry. In a rhesus monkey survivor of experimental Ebola virus (EBOV) infection, we observed and documented the clinical, virologic, immunologic, and histopathologic features of severe uveitis. Here we show the clinical natural history, resultant ocular pathology, intraocular antigen-specific antibody detection, and persistent intraocular EBOV RNA detected long after clinical resolution. The association of persistent EBOV RNA as a potential driver of severe immunopathology has pathophysiologic implications for understanding, preventing, and mitigating vision-threatening uveitis in EVD survivors.

Long-term consequences of food insecurity among Ebola virus disease-affected households after the 2013-2016 epidemic in rural communities of Kono District, Sierra Leone: A qualitative study.

The 2013-2016 Ebola virus disease (EVD) epidemic caused food insecurity during and immediately following local outbreaks in Sierra Leone, but longer-term effects are less well described, particularly among households with no EVD survivors. We conducted a qualitative sub-study in July 2018 in Kono District, Sierra Leone to understand the impact of food insecurity on EVD-affected households. Using data from a community-based cohort, we compiled a list of all households, within the sampled communities in Kono District, that had at least one EVD case during the epidemic. We used purposive sampling to recruit 30 households, inclusive of 10 households with no EVD survivors, to participate in the study. The research team conducted open-ended, semi-structured interviews with the head of each household. All 30 interviews were transcribed, translated, and analyzed using comparative content analysis consistent with a grounded theory approach. Most household members were facing persistent food insecurity as direct or indirect consequences of the EVD epidemic, regardless of whether they did or did not live with EVD survivors. Three major themes emerged as drivers and/or mitigators of EVD-related food insecurity. Financial instability and physical health complications were drivers of food insecurity in the population, whereas support provided by NGOs or governmental agencies was observed as a mitigator and driver of food insecurity after its removal. Among the EVD-households reporting long-term support through jobs and educational opportunities, there was sustained mitigation of food insecurity. EVD-affected households with and without survivors continue to face food insecurity three years after the EVD epidemic. Provision of support was a mitigator of food insecurity in the short term, but its removal was a driver of food insecurity in the longer term, suggesting the need for longer-term transitional support in affected households.

Relationship between selenium deficiency and vulnerability to ebolavirus disease in beni, drc

In Ebola patients, selenium aids in regulating blood clotting and possibly assist in coagulopathy properties of the Ebola haemorrhagic fever. Therefore, the objectives of this study were to determine the Selenium levels of people living in Beni, DRC and whether there is an association between Ebola vulnerability and selenium deficiency.This was a case control study with cases being Ebola virus disease survivors and controls were their contact persons during the time of infection. Students t-test were computed to determine if there exist a significant difference in the population means selenium levels in the case group and control group. Logistic regression analysis model was fitted into the data to determine the association between selenium deficiency and vulnerability to EVD adjusting for demographic and socio-economic factors.The mean difference in selenium levels of non - survivors was higher than that of survivors. A t-test conducted suggested that this difference in mean was statistically significant with p-value less than 0.05 (0.00181). The odds of getting infected by Ebola while having normal selenium levels, is 3.47 (confidence interval, 1.30 - 10.21) times higher than when one has high selenium levels after adjusting for all other covariates as mentioned above.There was a statistically significant relationship between Ebola vulnerability and selenium deficiency.

Statistical methodologies for evaluation of the rate of persistence of Ebola virus in semen of male survivors in Sierra Leone.

The 2013-2016 Ebola virus (EBOV) outbreak in West Africa was the largest and most complex outbreak ever, with a total number of cases and deaths higher than in all previous EBOV outbreaks combined. The outbreak was characterized by rapid spread of the infection in nations that were weakly prepared to handle it. EBOV ribonucleic acid (RNA) is known to persist in body fluids following disease recovery, and studying this persistence is crucial for controlling such epidemics. Observational cohort studies investigating EBOV persistence in semen require following up recently recovered survivors of Ebola virus disease (EVD), from recruitment to the time when their semen tests negative for EBOV, the endpoint being time-to-event. Because recruitment of EVD survivors takes place weeks or months following disease recovery, the event of interest may have already occurred. Survival analysis methods are the best suited for the estimation of the virus persistence in body fluids but must account for left- and interval-censoring present in the data, which is a more complex problem than that of presence of right censoring alone. Using the Sierra Leone Ebola Virus Persistence Study, we discuss study design issues, endpoint of interest and statistical methodologies for interval- and right-censored non-parametric and parametric survival modelling. Using the data from 203 EVD recruited survivors, we illustrate the performance of five different survival models for estimation of persistence of EBOV in semen. The interval censored survival analytic methods produced more precise estimates of EBOV persistence in semen and were more representative of the source population than the right censored ones. The potential to apply these methods is enhanced by increased availability of statistical software to handle interval censored survival data. These methods may be applicable to diseases of a similar nature where persistence estimation of pathogens is of interest.