A major nosological mistake in AIDS—meaning a fundamental error in how the disease is defined, classified, or diagnosed—could be the most consequential nosological error in history because of several deeply impactful social, scientific, and ethical consequences. Scale and Impact of AIDS The way AIDS was defined and classified determined how millions of people were diagnosed, treated, and socially perceived. Nosological mistakes have led to unnecessary suffering, stigmatization, discrimination, and sometimes fatal outcomes for entire populations. During the early epidemic, AIDS definitions dictated global policies, resource allocation, and public health strategies, impacting the lives of marginalized groups and shaping health systems globally. Misdirected Interventions and Suffering If the nosology—such as equating all immune compromise with AIDS or failing to recognize other causes—was incorrect, countless lives may have been lost or damaged due to misdiagnosis, inappropriate tre...