The purpose of this Notice of Funding Opportunity (NOFO) is to solicit applications focused on the neurological and/or mental health-related manifestations of infection-associated chronic illnesses, including the post-acute sequelae of COVID-19 (Neuro-PASC) as well as other chronic illnesses with a potential infectious trigger (post-treatment Lyme Disease, myalgic encephalomyelitis/chronic fatigue syndrome [ME/CFS], postural orthostatic tachycardia syndrome [POTS], post-viral fatigue syndromes, etc.). Projects that investigate common neurological and/or mental health-related mechanisms across multiple infection-associated chronic illnesses would be of particular interest, although this is not a requirement (i.e., applications can focus on a single condition). Neurologically focused clinical research investigating scientifically compelling pathways that contribute to the development of infection-associated chronic illnesses - including basic experimental studies in humans (BESH) or mechanistic clinical trials that will accelerate the development of effective treatments - are within the scope of this initiative. Preclinical studies utilizing animal, cell culture, and/or human tissue models are also encouraged. All applications must propose such studies in the context of a post-infectious etiology.