Developing bioinformatics approaches for the analysis of influenza virus whole genome sequence data

Influenza viruses represent a major public health burden worldwide, resulting in an estimated 500,000 deaths per year, with potential for devastating pandemics. Considerable effort is expended in the surveillance of influenza, including major World Health Organization (WHO) initiatives such as the Global Influenza Surveillance and Response System (GISRS). To this end, whole-genome sequencning (WGS), and corresponding bioinformatics pipelines, have emerged as powerful tools. However, due to the inherent diversity of influenza genomes, circulation in several different host species, and noise in short-read data, several pitfalls can appear during bioinformatics processing and analysis. 2.1.2 Results Conventional mapping approaches can be insufficient when a sub-optimal reference strain is chosen. For short-read datasets simulated from human-origin influenza H1N1 HA sequences, read recovery after single-reference mapping was routinely as low as 90% for human-origin influenza sequences, and often lower than 10% for those from avian hosts. To this end, I developed software using de Bruijn 47Graphs (DBGs) for classification of influenza WGS datasets: VAPOR. In real data benchmarking using 257 WGS read sets with corresponding de novo assemblies, VAPOR provided classifications for all samples with a mean of >99.8% identity to assembled contigs. This resulted in an increase of the number of mapped reads by 6.8% on average, up to a maximum of 13.3%. Additionally, using simulations, I demonstrate that classification from reads may be applied to detection of reassorted strains. 2.1.3 Conclusions The approach used in this study has the potential to simplify bioinformatics pipelines for surveillance, providing a novel method for detection of influenza strains of human and non-human origin directly from reads, minimization of potential data loss and bias associated with conventional mapping, and facilitating alignments that would otherwise require slow de novo assembly. Whilst with expertise and time these pitfalls can largely be avoided, with pre-classification they are remedied in a single step. Furthermore, this algorithm could be adapted in future to surveillance of other RNA viruses. VAPOR is available at https://github.com/connor-lab/vapor. Lastly, VAPOR could be improved by future implementation in C++, and should employ more efficient methods for DBG representation