Embodiments are directed to systems and methods for pathogen detection using next-generation sequencing (NGS) analysis of a sample. Embodiments may apply alignment algorithms (e.g., SNAP and/or RAPSearch alignment algorithms) to align individual sequence reads from a sample in a next-generation sequencing (NGS) dataset against reference genome entries in a classified reference genome database. Embodiments of the present invention may include classifying, filtering, and displaying results to a clinician that can then quickly and easily obtain the results of the sequencing to identify a pathogen or other genetic material in a sample that is being tested. A negative sample and a corresponding database can be used to remove contaminants from a list of candidate pathogens. Thus, embodiments are directed to a system that is configured to filter the results of a sequencing alignment and classify a sample quickly.