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This final report updates preliminary data on an attenuated, replication-competent, recombinant vesicular stomatitis virus–based vaccine candidate designed to prevent Ebola virus disease. The results supported the safety and immunogenicity of up to two doses of the vaccine. The worst Ebola virus disease (EVD) outbreak in recorded history has resulted in more than 28,000 cases and 11,000 reported deaths. 1 Although the primary strategy to stop the transmission of Ebola remains the identification and isolation of contacts and the use of appropriate personal protective equipment, the development of a safe and efficacious vaccine would provide an important public health tool. Numerous Ebola virus vaccine candidates are in preclinical development, and some have proceeded to human trials. 2 – 5 An Ebola virus vaccine candidate based on an attenuated, replication-competent, recombinant vesicular stomatitis virus (rVSV) has shown promise in preclinical studies. The . . .

Ebola virus causes a devastating clinical illness that is associated with high mortality. In this trial conducted primarily in West Africa during an outbreak, ZMapp (a cocktail of three monoclonal antibodies against Ebola) showed some clinical activity. The 2014–2016 Ebola outbreak in West Africa was unprecedented in sheer scope, duration, and number of human casualties. 1 , 2 The outbreak resulted in more than 28,000 suspected or confirmed cases of Ebola virus disease (EVD) and more than 11,000 deaths. 3 Fragile health care infrastructures that were often already severely compromised by past years of civil strife played a substantial role in the propagation of the outbreak. Although the final postmortem analysis of the global response has yet to be written, there can be little doubt that the lack of therapeutic agents and vaccines with proven efficacy against EVD further contributed . . .

In this set of four phase 1 studies, a recombinant vesicular stomatitis virus (rVSV)–based Ebola vaccine induced Ebola virus–specific immune responses and was associated with side effects that included fever and transient arthritis, rash, and VSV viremia. In August 2014, after the outbreak of Ebola virus disease was declared a public health emergency of international concern by the World Health Organization (WHO), the Canadian government donated 800 vials of the replication-competent recombinant vesicular stomatitis virus (rVSV)–vectored Zaire ebolavirus (rVSV-ZEBOV) candidate vaccine to the WHO. The VSV Ebola Consortium (VEBCON) was created under the auspices of the WHO to initiate phase 1 studies to facilitate rapid progression to phase 2 and 3 trials in affected countries. 1 Live replicating viral vaccines elicit humoral and cellular immune responses against viral pathogens. 2 , 3 A single injection of 10 million plaque-forming units . . .

An association between malaria and risk for death among patients with Ebola virus disease has suggested within-host interactions between Plasmodium falciparum parasites and Ebola virus. To determine whether such an interaction might also influence the probability of acquiring either infection, we used a large snapshot surveillance study from rural Gabon to test if past exposure to Ebola virus is associated with current infection with Plasmodium spp. during nonepidemic conditions. We found a strong positive association, on population and individual levels, between seropositivity for antibodies against Ebola virus and the presence of Plasmodium parasites in the blood. According to a multiple regression model accounting for other key variables, antibodies against Ebola virus emerged as the strongest individual-level risk factor for acquiring malaria. Our results suggest that within-host interactions between malaria parasites and Ebola virus may underlie epidemiologic associations.

In March 2014, an outbreak of Ebola virus disease associated with a high fatality rate was identified in Guinea, with evidence of ongoing person-to-person transmission. In this update to the preliminary report, the virus is found to be a new strain related to Zaire ebolavirus . Outbreaks caused by viruses of the genera ebolavirus and marburgvirus represent a major public health issue in sub-Saharan Africa. Ebola virus disease is associated with a case fatality rate of 30 to 90%, depending on the virus species. Specific conditions in hospitals and communities in Africa facilitate the spread of the disease from human to human. Three ebolavirus species have caused large outbreaks in sub-Saharan Africa: EBOV, Sudan ebolavirus, and the recently described Bundibugyo ebolavirus . 1 , 2 Epidemics have occurred in the Democratic Republic of Congo, Sudan, Gabon, Republic of Congo, and Uganda. Reston ebolavirus circulates in the Philippines. It . . .

Ebola virus has been detected in the semen of men after their recovery from Ebola virus disease (EVD). We report the presence of Ebola virus RNA in semen in a cohort of survivors of EVD in Sierra Leone. We enrolled a convenience sample of 220 adult male survivors of EVD in Sierra Leone, at various times after discharge from an Ebola treatment unit (ETU), in two phases (100 participants were in phase 1, and 120 in phase 2). Semen specimens obtained at baseline were tested by means of a quantitative reverse-transcriptase-polymerase-chain-reaction (RT-PCR) assay with the use of the target sequences of NP and VP40 (in phase 1) or NP and GP (in phase 2). This study did not evaluate directly the risk of sexual transmission of EVD. Of 210 participants who provided an initial semen specimen for analysis, 57 (27%) had positive results on quantitative RT-PCR. Ebola virus RNA was detected in the semen of all 7 men with a specimen obtained within 3 months after ETU discharge, in 26 of 42 (62%) with a specimen obtained at 4 to 6 months, in 15 of 60 (25%) with a specimen obtained at 7 to 9 months, in 4 of 26 (15%) with a specimen obtained at 10 to 12 months, in 4 of 38 (11%) with a specimen obtained at 13 to 15 months, in 1 of 25 (4%) with a specimen obtained at 16 to 18 months, and in no men with a specimen obtained at 19 months or later. Among the 46 participants with a positive result in phase 1, the median baseline cycle-threshold values (higher values indicate lower RNA values) for the NP and VP40 targets were lower within 3 months after ETU discharge (32.4 and 31.3, respectively; in 7 men) than at 4 to 6 months (34.3 and 33.1; in 25), at 7 to 9 months (37.4 and 36.6; in 13), and at 10 to 12 months (37.7 and 36.9; in 1). In phase 2, a total of 11 participants had positive results for NP and GP targets (samples obtained at 4.1 to 15.7 months after ETU discharge); cycle-threshold values ranged from 32.7 to 38.0 for NP and from 31.1 to 37.7 for GP. These data showed the long-term presence of Ebola virus RNA in semen and declining persistence with increasing time after ETU discharge. (Funded by the World Health Organization and others.).

In its largest outbreak, Ebola virus disease is spreading through Guinea, Liberia, Sierra Leone, and Nigeria. We sequenced 99 Ebola virus genomes from 78 patients in Sierra Leone to ~2000× coverage. We observed a rapid accumulation of interhost and intrahost genetic variation, allowing us to characterize patterns of viral transmission over the initial weeks of the epidemic. This West African variant likely diverged from central African lineages around 2004, crossed from Guinea to Sierra Leone in May 2014, and has exhibited sustained human-to-human transmission subsequently, with no evidence of additional zoonotic sources. Because many of the mutations alter protein sequences and other biologically meaningful targets, they should be monitored for impact on diagnostics, vaccines, and therapies critical to outbreak response.

This case report presents evidence of sexual transmission of Ebola virus from a man to a woman, nearly 200 days after the initial illness in the man. In December 2013, EBOV emerged in Guinea and quickly spread to several neighboring countries, resulting in the largest recorded outbreak of EVD in history. 1 On September 3, 2015, Liberia was declared to be free from EVD for the second time, and although new cases were still being reported in Guinea and Sierra Leone as of September 9, 2015, weekly numbers were just a fraction of those reported during the peak of the outbreak. 1 As the EVD outbreak in western Africa wanes, the affected countries must transition from controlling an EVD epidemic to addressing the needs of an unprecedented number of . . .

The 2013–2016 West African epidemic caused by the Ebola virus was of unprecedented magnitude, duration and impact. Here we reconstruct the dispersal, proliferation and decline of Ebola virus throughout the region by analysing 1,610 Ebola virus genomes, which represent over 5% of the known cases. We test the association of geography, climate and demography with viral movement among administrative regions, inferring a classic ‘gravity’ model, with intense dispersal between larger and closer populations. Despite attenuation of international dispersal after border closures, cross-border transmission had already sown the seeds for an international epidemic, rendering these measures ineffective at curbing the epidemic. We address why the epidemic did not spread into neighbouring countries, showing that these countries were susceptible to substantial outbreaks but at lower risk of introductions. Finally, we reveal that this large epidemic was a heterogeneous and spatially dissociated collection of transmission clusters of varying size, duration and connectivity. These insights will help to inform interventions in future epidemics. Frequent dispersal and short-lived local transmission clusters fuelled the 2013–2016 Ebola virus epidemic in Guinea, Liberia and Sierra Leone. Evolution of an epidemic Understanding how and why viruses spread during epidemics is crucial for planning how to prevent and respond to future threats. Andrew Rambaut and colleagues provide an overview of the genetic epidemiology of the 2013–2016 epidemic caused by Ebola virus in West Africa. By analysing more than 1,600 Ebola virus genomes, the authors determine the factors that were important in the spread of the epidemic and also explain why the virus did not spread into neighbouring countries.

Seven years after the declaration of the first epidemic of Ebola virus disease in Guinea, the country faced a new outbreak—between 14 February and 19 June 2021—near the epicentre of the previous epidemic 1 , 2 . Here we use next-generation sequencing to generate complete or near-complete genomes of Zaire ebolavirus from samples obtained from 12 different patients. These genomes form a well-supported phylogenetic cluster with genomes from the previous outbreak, which indicates that the new outbreak was not the result of a new spillover event from an animal reservoir. The 2021 lineage shows considerably lower divergence than would be expected during sustained human-to-human transmission, which suggests a persistent infection with reduced replication or a period of latency. The resurgence of Zaire ebolavirus from humans five years after the end of the previous outbreak of Ebola virus disease reinforces the need for long-term medical and social care for patients who survive the disease, to reduce the risk of re-emergence and to prevent further stigmatization. The viral lineage responsible for the February 2021 outbreak of Ebola virus disease in Guinea is nested within a clade that predominantly consists of genomes sampled during the 2013–2016 epidemic, suggesting that the virus might have re-emerged after a long period of latency within a previously infected individual.