In March 2014, Kenema Government Hospital (KGH) established EBOV surveillance in Kenema, Sierra Leone, near the origin of
the 2014 outbreak (Fig. 1C and fig. S1) (6). Following standards for field-based tests in previous (7) and current (3) outbreaks, KGH performed conventional PCR-based EBOV diagnostics (8)
(fig. S2); all tests were negative through early May. On May 25, KGH
scientists confirmed the first case of EVD in Sierra
Leone.
Samaa kombinaatiota käytettiin seuraavassa ryhmässä, johon kuului 84 näytettä 66 muusta potilaasta ja tehtiin kaksi toisistaan riippumatonta replikaattia jokaisesta näytteestä ( Kuva 1D).
Lisäksi sekvensoitiin 35 näytettä epäillyistä EVD- tapauksista, jotka oli testattu negatiivisiksi ebolaviruksen (EBOV) suhteen ja genominen analyysi paljastikin näissä joitain muita tunnettuja patogeenejä kuten Lassa virusta, HIV-1 virusta, Enterovirusta A ja malariaparasiittia ( Kuva S3).
We evaluated four independent library preparation methods and two sequencing platforms (9)
(table S1) for our first batch of 15 inactivated EVD samples from 12
patients. Nextera library construction and Illumina
sequencing provided the most complete genome
assembly and reliable intrahost single nucleotide variant (iSNV,
frequency >0.5%)
identification (6).
We used this combination for a second batch of 84 samples from 66 additional patients, performing two independent replicates from each sample (Fig. 1D). We also sequenced 35 samples from suspected EVD cases that tested negative for EBOV; genomic analysis identified other known pathogens, including Lassa virus, HIV-1, enterovirus A and malaria parasites (fig. S3).
We used this combination for a second batch of 84 samples from 66 additional patients, performing two independent replicates from each sample (Fig. 1D). We also sequenced 35 samples from suspected EVD cases that tested negative for EBOV; genomic analysis identified other known pathogens, including Lassa virus, HIV-1, enterovirus A and malaria parasites (fig. S3).
In total, we generated 99 EBOV genome
sequences from 78 confirmed EVD patients, representing over 70% of the
EVD patients
diagnosed in Sierra Leone in late May to mid June;
we employed multiple extraction methods or timepoints for 13 patients
(table
S2). Median coverage was >2,000x, spanning more
than 99.9% of EBOV coding regions (Fig. 1, D and E, and table S2).
Deep-sequence coverage allowed identification of 263 iSNVs (73 nonsynonymous, 108 synonymous, 70 noncoding, and 12 frameshift) in the Sierra Leone patients (6). For all patients with multiple time points, consensus sequences were identical and iSNV frequencies remained stable (fig. S4). One notable intrahost variation is the RNA editing site of the glycoprotein (GP) gene (fig. S5A) (10–12), which we characterize in patients (6).
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