Using Whole Genome Sequences to Investigate Adenovirus Outbreaks, Including Five Deaths in a Haematopoietic Stem Cell Transplant Unit

Abstract

AbstractBackgroundHuman mastadenoviruses (HAdV) are associated with significant morbidity and mortality amongst the immunocompromised population. A recent surge in HAdV cases, including five deaths, amongst a haematopoietic stem cell transplant population led us to use whole genome sequencing (WGS) to investigate.MethodsTo gain a complete transmission picture, we compared outbreak and non-outbreak sequences (54 sequences from 37 patients) with GenBank sequences and our own database of previously sequenced HAdVs (132 sequences from 37 patients). An improved bait set for WGS was used. Maximum likelihood trees and pairwise differences were used to evaluate genotypic relationships paired with epidemiological data from routine Infection, Prevention and Control (IPC) activity.ResultsNine monophyletic clusters were identified, seven of which were corroborated by epidemiological evidence and by comparison of single nucleotide polymorphisms. Two incomplete patient clusters were identified by IPC over the same time period. Of the five patients who died, one had a mixed HAdV infection and two were the source of transmission events.ConclusionsThe clinical consequences of unmitigated HAdV transmission events are high. Focusing on two high risk wards using WGS we identified six transmission events, over prolonged periods, that would have gone unnoticed using traditional polymerase chain reaction and epidemiology. Mixed infection is frequent (10% of patients), providing a sentinel source of recombination and superinfection. Immunosuppressed patients harbouring a high rate of HAdV positivity require comprehensive surveillance. As a consequence of these findings, HAdV WGS is being incorporated routinely into a clinical algorithm to prevent transmission and influence IPC policy in real-time.SummaryWhole genome sequencing of adenovirus, direct from clinical samples, can be used to identify cryptic health care associated transmission events, and to resolve transmission suspected by traditional epidemiology. It can also identify mixed genotype infections in immunocompromised patient populations.