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. 2018 Mar 28;217(8):1214-1221.
doi: 10.1093/infdis/jiy004.

Anatomy of a Hotspot: Chain and Seroepidemiology of Ebola Virus Transmission, Sukudu, Sierra Leone, 2015-16

J Daniel Kelly  1   2 , Mohamed Bailor Barrie  2   3 , Annelies W Mesman  2 , Sahr Karku  2 , Komba Quiwa  2 , Michael Drasher  2 , Gabriel Warren Schlough  2 , Kerry Dierberg  2 , Songor Koedoyoma  4 , Christina P Lindan  5 , James Holland Jones  6 , Gabriel Chamie  7 , Lee Worden  8 , Bryan Greenhouse  7 , Sheri D Weiser  7 , Travis C Porco  5 , George W Rutherford  5 , Eugene T Richardson  2   3   9   10
Affiliations

Anatomy of a Hotspot: Chain and Seroepidemiology of Ebola Virus Transmission, Sukudu, Sierra Leone, 2015-16

J Daniel Kelly et al. J Infect Dis. .

Abstract

Studies have yet to include minimally symptomatic Ebola virus (EBOV) infections and unrecognized Ebola virus disease (EVD) in Ebola-related transmission chains and epidemiologic risk estimates. We conducted a cross-sectional, sero-epidemiological survey from October 2015 to January 2016 among 221 individuals living in quarantined households from November 2014 to February 2015 during the Ebola outbreak in the village of Sukudu, Sierra Leone. Of 48 EBOV-infected persons, 25% (95% confidence interval [CI], 14%-40%) had minimally symptomatic EBOV infections and 4% (95% CI, 1%-14%) were unrecognized EVD cases. The pattern of minimally symptomatic EBOV infections in the transmission chain was nonrandom (P < .001, permutation test). Not having lived in the same house as an EVD case was significantly associated with minimally symptomatic infection. This is the first study to investigate a chain of EBOV transmission inclusive of minimally symptomatic EBOV infections and unrecognized EVD. Our findings provide new insights into Ebola transmission dynamics and quarantine practices.

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Figures

Figure 1.
Figure 1.
Satellite image of village. Quarantined areas are bounded in red, public latrines in yellow. Source: Google Earth Pro. (Inset: Sierra Leone, Liberia, and Guinea; Kono District in red. Source: Centers for Disease Control and Prevention.)
Figure 2.
Figure 2.
A flow diagram of Ebola virus transmission among the 221 quarantined persons. Abbreviations: EBOV, Ebola virus; EVD, Ebola virus disease.
Figure 3.
Figure 3.
A geospatial representation of the chain of Ebola virus (EBOV) transmission. The cluster size of 48 EBOV-infected persons in Sukudu orginated from the Ebola virus disease (EVD) index case (center: gray circle) in Koidu Town, Kono District, Sierra Leone. Small circles represent the reported EVD cases, large circles represent unrecognized EVD cases, and diamonds represent minimally symptomatic EBOV-infected persons. Arrows demonstrate the directionality of the EBOV transmission between persons and epidemiological type of link. Black arrows represent type 1 links, solid gray arrows represent type 2 links, and dashed grey arrows represent type 3 links. Color describes the households in which persons acquired EBOV.
Figure 4.
Figure 4.
A temporal representation of the chain of transmission and epidemic curve for Ebola virus disease (EVD) cases. The EVD index case (left: gray circle) in Koidu Town initiated a chain of 34 reported EVD cases in Sukudu. Each circle represents the date of onset of EVD symptoms reported for each reported EVD case. Arrows demonstrate the directionality of the Ebola virus (EBOV) transmission between persons. Solid black arrows represent the primary contact of the EVD case, and red arrows represent secondary contacts. Color describes the households of EVD cases. We excluded the minimally symptomatic EBOV-infected persons and unrecognized EVD cases because they were assumed to be noninfectious or were not asked to recall their date of symptom onset.
See this image and copyright information in PMC

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