Analysis of 14.4 billion insurance claims from 244.7 million Americans reveals that most long COVID symptoms attributed to the virus stem from testing bias rather than actual infection effects. The study found people with existing health conditions were more likely to seek COVID testing, leading researchers to mistakenly attribute their pre-existing symptoms to the virus. Using a novel design comparing patients whose first COVID test was positive versus negative, researchers identified genuine long COVID effects across respiratory, cardiovascular, musculoskeletal, and skin systems—but at rates an order of magnitude lower than conventional studies suggested. The findings indicate long COVID symptoms persist up to one year but not beyond, with post-one-year symptoms occurring at similar rates in both COVID-positive and negative groups. This represents a major recalibration of long COVID's true burden, suggesting millions fewer Americans may be experiencing genuine post-viral symptoms than previously estimated. However, as this preprint awaits peer review, these paradigm-shifting findings require independent validation before reshaping clinical practice. The methodology could transform how researchers study post-infectious syndromes by accounting for healthcare-seeking behaviors that bias traditional observational studies.