PROJECT SUMMARY This study is the culmination of years of careful preliminary work spent developing and validating a versatile CWGA workflow that both improves upon the quality and reliability of available Leptospira genome data and is capable of producing (and analyzing) these data directly from clinical samples — a crucial advance, as most current studies avoid the cost of Leptospira culture. Crucial gaps in our understanding of Leptospira virulence and pathogenetic mechanisms of disease persist due to the restricted scope, debatable quality and inherent bias of publicly available genome data that blunt the power of CWGA. Our first objective here is to apply this new approach to SMS data generated from a large biobank of 592 de-identified acute human serum samples (with relevant demographic, clinical and epidemiological metadata) to identify Leptospira genes, with appropriate sample distribution linked, linked to severe complications and poor outcomes (and) of human leptospirosis presuming that these include reliable diagnostic targets and risk assessment markers (“prognostic indicators”). Biobank sera originate from a recent NIH/NIIAID-funded prospective study of human leptospirosis in Sri Lanka and include >400 from laboratory confirmed leptospirosis cases from which we obtained 25 Leptospira isolates belonging to 5 discrete species and comprising at least 12 previously unreported serotypes. The low culture success rate (<6%) — further confirmation of the desperate need for analytical tools that avoid Leptospira culture — prompted development of a culture independent CWGA workflow featured in the current study. Next, reliable candidate genes so identified will be used as substrates for qPCR assay development with subsequent cross validation against a second large biobank of unrelated sera derived from a recent flood associated outbreak of leptospirosis in Puerto Rico. Our success here should lay the groundwork for rapid development of antigen-detection diagnostic tests and would have an immediate and profound impact on the Leptospira field. Moreover, untethered from the inefficiency and bias of Leptospira culture, CWGA offers unprecedented insight into fundamental Leptospira biology.