On February 7th 2021, the DRC Ministry of Health announced a confirmed case of Ebola virus disease (EVD) in the North Kivu Province of the Democratic Republic of Congo (DRC). Sequencing results from samples sent to Institut National de Recherche Biomédicale (INRB) in Kinshasa confirmed these new cases were caused by Zaire ebolavirus and were linked to some form of viral persistence within a survivor of the 2018-2020 EVD outbreak in North Kivu, which was the largest outbreak in DRC’s history.
Less than a week later, samples sent to the national laboratory in Conakry were also confirmed positive for EVD, and on February 14th the Guinea Ministry of Health officially declared an outbreak of EVD in the N'Zérékoré Prefecture. Institut Pasteur de Dakar (IP Dakar) and Centre de Recherche et de Formation en Infectiologie de Guineé (CERFIG) in Conakry completed viral sequencing from four clinical samples, confirming the outbreak was caused by Zaire ebolavirus. In addition, given the limited number of mutations accumulated relative to viruses from the 2014 to 2016 West Africa outbreak, they concluded that the initiation of this 2021 outbreak was most likely a result of viral persistence (sexual transmission or recrudescence) in a survivor of the West Africa outbreak. In a paradigm shift for filovirus research, this finding would push the longest known period of viral persistence from 500 days to 5-7 years. However, the lack of data about the rate of mutation of the virus in its animal host means there is still the possibility this outbreak was caused by a new introduction from an animal reservoir.
BARDA and its interagency partners quickly jumped into the response for these new outbreaks. By the end of April, 1,989 individuals, including 542 front-line workers, in DRC were vaccinated with the Ebola vaccine ErveboTM (rVSV-ZEBOV), and eight confirmed cases received monoclonal antibody therapeutics InmazebTM or EbangaTM (6/8 recovered). In Guinea, 10,833 individuals were vaccinated (including 2,876 front line workers) by the end of May and eight patients received InmazebTM (8/8 recovered). The critical role that BARDA supported products played in the 2021 DRC and Guinea outbreaks is clear. Ring vaccination efforts limited transmission and the case fatality rates among patients receiving the FDA approved Ebola therapeutics InmazebTM or EbangaTM were reduced to 25% in the DRC and 0% in Guinea.
On May 3rd, the Ministry of Health of the DRC declared the end of human-to-human transmission of EVD over in North Kivu Province as more than 42 days (two maximum incubation periods) had elapsed since the date of the second consecutive negative test of the last confirmed case. In this outbreak, there was a total of 12 cases (11 confirmed, 1 probable), and six deaths (case-fatality proportion = 50.0%). Shortly thereafter on June 19th, the Guinea Ministry of Health and WHO announced the Guinea outbreak was over as well. There was a total of 23 cases (16 confirmed, 7 probable), and 12 deaths (case-fatality proportion = 52.2%).
BARDA/CBRN’s objective for the development of Ebola medical countermeasures is to
i) develop vaccines to reduce transmission of this deadly virus and protect healthcare workers, contacts and the communities at large, and
ii) develop drugs to provide healthcare workers with a strong therapeutic intervention to complement the supportive care available in Ebola treatment units and increase the patients’ chance for survival.
The 2014-2016 West Africa outbreak and the 2018-2020 Eastern DRC outbreaks combined to infect over 30,000 people, over 13,000 of whom ultimately succumbed to the disease. In contrast, the 2021 responses have had the benefit of a strong medical countermeasure arsenal to complement the evolving and improving infection prevention and control measures implemented by our USG and global partners. We are cautiously optimistic that the rapid containment of the 2021 outbreaks in the DRC and Guinea is indicative of coming successes as we move swiftly to stop future outbreaks.
References:
1. Release - 4 EBOV genomes from Guinea 2021 outbreak
2. Resurgence of Ebola Virus Disease in Guinea Linked to a Survivor With Virus Persistence in Seminal Fluid for More Than 500 Days