Dokubo EK, et al. - After the end of widespread transmission in Liberia, identification of the Ebola virus disease cluster in November 2015, after a 15-year-old boy tested positive for Ebola virus infection in Monrovia, led researchers to perform epidemiological and laboratory investigations ascertaining the source of infection for the cluster of Ebola virus disease cases, and assessing possible transmission scenarios. This investigation provides evidence suggesting the persistence of Ebola virus and highlighting the risk for outbreaks after interruption of active transmission. Findings thereby emphasize the necessity for focused prevention efforts among survivors and sustained capacity to rapidly detect and respond to new Ebola virus disease cases to prevent recurrence of a widespread outbreak.

Methods

• Researchers conducted case investigations to assess previous contact with cases of Ebola virus disease or infection with Ebola virus.
• They performed molecular investigations on blood samples to explore a potential linkage between Ebola virus isolated from cases in this November 2015, cluster and epidemiologically linked cases from the 2014–15 west African outbreak, according to the national case database.

Results

• The family of the index case (mother, father, three siblings) comprised the cluster investigated.
• Within the LB5 sublineage that circulated in Liberia starting around August 2014, phylogenetically associated Ebola virus genomes assembled from two cases in the November 2015, cluster, and an epidemiologically linked Ebola virus disease case in July 2014, were identified.
• With placement in the LB5 sublineage, partial genomes from two additional individuals were also consistent, one from each cluster.
• Infection with a lineage of the virus from a former transmission chain in the country was suggested by the sequencing data.
• The most plausible scenario suggested by the serology and epidemiological and genomic data was that a female case in the November 2015, cluster survived Ebola virus disease in 2014, had viral persistence or recurrent disease and transmitted the virus to three family members a year later.