While the major 2014-2015 outbreak of Ebolavirus disease in west Africa ceased following control measures, subsequent clusters of infection still occurred in the region. Such a cluster was identified in November 2015 in Liberia after a 15-year-old boy tested positive for Ebolavirus infection in Monrovia and raised the possibility of transmission from a persistently infected patient. The authors performed case investigations to ascertain previous contact with cases of Ebolavirus disease or infection with Ebolavirus. Molecular techniques were performed on blood samples to explore a potential linkage between viruses isolated from cases in this cluster and epidemiologically linked cases from the outbreak. The cluster investigated was the family of the index case (mother, father and three siblings). Ebolavirus genomes were sequenced and assembled from two of these cases and from an epidemiologically linked Ebolavirus disease case originating from July 2014, and were found to be phylogenetically related within the LB5 sublineage that circulated in Liberia from around August 2014. Partial genomes from two additional patients, one from each cluster, were also consistent with placement in the LB5 sublineage. The sequencing data suggest that infection occurred with a lineage of the virus from a former transmission chain in the country. Based on serology and this epidemiologic and genomic data, the authors hypothesised that a female case in the November 2015 cluster survived Ebolavirus disease in 2014, had viral persistence or recurrent disease and transmitted the virus to three family members a year later. Therefore the study of this cluster suggests that Ebolavirus can persist, leading to a risk of outbreaks after interruption of active transmission.
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