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Molecular evolution in court: analysis of a large hepatitis C virus outbreak from an evolving source.

González-Candelas F, Bracho MA, Wróbel B, Moya A - BMC Biol. (2013)

Bottom Line: The date turned out to be 10 years before the detection of the outbreak.The number of patients infected was small at first, but it increased substantially in the months before the detection of the outbreak.We have developed a procedure to integrate molecular phylogenetic reconstructions of rapidly evolving viral populations into a forensic setting adequate for molecular epidemiological analysis of outbreaks and transmission events.

View Article: PubMed Central - HTML - PubMed

Affiliation: Joint Research Unit Genómica y Salud CSISP (FISABIO), Instituto Cavanilles/Universidad de Valencia, Paterna, Valencia, Spain. fernando.gonzalez@uv.es

ABSTRACT

Background: Molecular phylogenetic analyses are used increasingly in the epidemiological investigation of outbreaks and transmission cases involving rapidly evolving RNA viruses. Here, we present the results of such an analysis that contributed to the conviction of an anesthetist as being responsible for the infection of 275 of his patients with hepatitis C virus.

Results: We obtained sequences of the NS5B and E1-E2 regions in the viral genome for 322 patients suspected to have been infected by the doctor, and for 44 local, unrelated controls. The analysis of 4,184 cloned sequences of the E1-E2 region allowed us to exclude 47 patients from the outbreak. A subset of patients had known dates of infection. We used these data to calibrate a relaxed molecular clock and to determine a rough estimate of the time of infection for each patient. A similar analysis led to an estimate for the time of infection of the source. The date turned out to be 10 years before the detection of the outbreak. The number of patients infected was small at first, but it increased substantially in the months before the detection of the outbreak.

Conclusions: We have developed a procedure to integrate molecular phylogenetic reconstructions of rapidly evolving viral populations into a forensic setting adequate for molecular epidemiological analysis of outbreaks and transmission events. We applied this procedure to a large outbreak of hepatitis C virus caused by a single source and the results obtained played a key role in the trial that led to the conviction of the suspected source.

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Neighbor-joining tree obtained with the NS5B-region sequences of hepatitis C virus (HCV)-1a samples analyzed in this study. Color codes: outbreak sequences are in black, red, and green (see legend to Figure 3), excluded from the outbreak are in dark purple, and local unrelated controls are in gray. The presumed source (PS) sequence is shown in blue. No clade was found with bootstrap support higher than 70%.
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Figure 2: Neighbor-joining tree obtained with the NS5B-region sequences of hepatitis C virus (HCV)-1a samples analyzed in this study. Color codes: outbreak sequences are in black, red, and green (see legend to Figure 3), excluded from the outbreak are in dark purple, and local unrelated controls are in gray. The presumed source (PS) sequence is shown in blue. No clade was found with bootstrap support higher than 70%.

Mentions: Neighbor-joining and maximum likelihood phylogenetic trees obtained from the NS5B sequences failed to group all the control samples in a monophyletic group (Figure 2). Furthermore, none of the nodes in the phylogenetic tree received a bootstrap support higher than 70% by either phylogenetic reconstruction method. This is not surprising considering that NS5B evolves much more slowly than other regions in the HCV genome (especially the E1-E2 region) and the relatively short sequence length analyzed. As a consequence, the phylogenetic signal in this region was too low to reliably separate the local controls, the patients infected from a common source and the patients infected from alternative sources.


Molecular evolution in court: analysis of a large hepatitis C virus outbreak from an evolving source.

González-Candelas F, Bracho MA, Wróbel B, Moya A - BMC Biol. (2013)

Neighbor-joining tree obtained with the NS5B-region sequences of hepatitis C virus (HCV)-1a samples analyzed in this study. Color codes: outbreak sequences are in black, red, and green (see legend to Figure 3), excluded from the outbreak are in dark purple, and local unrelated controls are in gray. The presumed source (PS) sequence is shown in blue. No clade was found with bootstrap support higher than 70%.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3717074&req=5

Figure 2: Neighbor-joining tree obtained with the NS5B-region sequences of hepatitis C virus (HCV)-1a samples analyzed in this study. Color codes: outbreak sequences are in black, red, and green (see legend to Figure 3), excluded from the outbreak are in dark purple, and local unrelated controls are in gray. The presumed source (PS) sequence is shown in blue. No clade was found with bootstrap support higher than 70%.
Mentions: Neighbor-joining and maximum likelihood phylogenetic trees obtained from the NS5B sequences failed to group all the control samples in a monophyletic group (Figure 2). Furthermore, none of the nodes in the phylogenetic tree received a bootstrap support higher than 70% by either phylogenetic reconstruction method. This is not surprising considering that NS5B evolves much more slowly than other regions in the HCV genome (especially the E1-E2 region) and the relatively short sequence length analyzed. As a consequence, the phylogenetic signal in this region was too low to reliably separate the local controls, the patients infected from a common source and the patients infected from alternative sources.

Bottom Line: The date turned out to be 10 years before the detection of the outbreak.The number of patients infected was small at first, but it increased substantially in the months before the detection of the outbreak.We have developed a procedure to integrate molecular phylogenetic reconstructions of rapidly evolving viral populations into a forensic setting adequate for molecular epidemiological analysis of outbreaks and transmission events.

View Article: PubMed Central - HTML - PubMed

Affiliation: Joint Research Unit Genómica y Salud CSISP (FISABIO), Instituto Cavanilles/Universidad de Valencia, Paterna, Valencia, Spain. fernando.gonzalez@uv.es

ABSTRACT

Background: Molecular phylogenetic analyses are used increasingly in the epidemiological investigation of outbreaks and transmission cases involving rapidly evolving RNA viruses. Here, we present the results of such an analysis that contributed to the conviction of an anesthetist as being responsible for the infection of 275 of his patients with hepatitis C virus.

Results: We obtained sequences of the NS5B and E1-E2 regions in the viral genome for 322 patients suspected to have been infected by the doctor, and for 44 local, unrelated controls. The analysis of 4,184 cloned sequences of the E1-E2 region allowed us to exclude 47 patients from the outbreak. A subset of patients had known dates of infection. We used these data to calibrate a relaxed molecular clock and to determine a rough estimate of the time of infection for each patient. A similar analysis led to an estimate for the time of infection of the source. The date turned out to be 10 years before the detection of the outbreak. The number of patients infected was small at first, but it increased substantially in the months before the detection of the outbreak.

Conclusions: We have developed a procedure to integrate molecular phylogenetic reconstructions of rapidly evolving viral populations into a forensic setting adequate for molecular epidemiological analysis of outbreaks and transmission events. We applied this procedure to a large outbreak of hepatitis C virus caused by a single source and the results obtained played a key role in the trial that led to the conviction of the suspected source.

Show MeSH
Related in: MedlinePlus