The investigators will characterize and compare protein signatures between groups with and without post-infection irritable bowel syndrome (PI-IBS). From previous Healthy Nevada Project (HNP) participants, at least 60 patients with PI-IBS and 60 healthy controls will undergo additional proteomics testing, age, sex and race/ethnicity-matched healthy. The investigators will use proteomic testing to detect, quantify and characterize serum protein biomarkers and protein signatures, and compare biomarkers and signatures between the patient groups of interest. Serum samples will be analyzed by the Nevada Proteomics Center. Samples will first undergo protein digestion, then peptides are separated using liquid chromatography (LC), mass spectral analysis is performed using an Orbitrap Eclipse mass spectrometer (Thermo Scientific, San Jose, CA) using data-independent acquisition (DIA). Library generation and data analysis will be performed using Spectronaut software (Biognosys, Schlieren, Switzerland). The Nevada Proteomics Center and Bioinformatics Center will be engaged during the data analyses comparing biomarkers and signatures between the patient groups of interest. This research aim has the potential to add to our understanding of the underlying mechanisms of PI-IBS and to create reliable differentiating protein biomarkers to better diagnose PI-IBS.