text: Long COVID or Post acute Sequelae of COVID 19 PASC An Overview of Biological Factors That May Contribute to Persistent Symptoms The novel virus severe acute respiratory syndrome coronavirus 2 SARS CoV 2 has caused a pandemic of coronavirus disease 2019 COVID 19 Across the globe a subset of patients who sustain an acute SARS CoV 2 infection are developing a wide range of persistent symptoms that do not resolve over the course of many months These patients are being given the diagnosis Long COVID or Post acute sequelae of COVID 19 PASC It is likely that individual patients with a PASC diagnosis have different underlying biological factors driving their symptoms none of which are mutually exclusive This paper details mechanisms by which RNA viruses beyond just SARS CoV 2 have be connected to long term health consequences It also reviews literature on acute COVID 19 and other virus initiated chronic syndromes such as post Ebola syndrome or myalgic encephalomyelitis chronic fatigue syndrome ME CFS to discuss different scenarios for PASC symptom development Potential contributors to PASC symptoms include consequences from acute SARS CoV 2 injury to one or multiple organs persistent reservoirs of SARS CoV 2 in certain tissues re activation of neurotrophic pathogens such as herpesviruses under conditions of COVID 19 immune dysregulation SARS CoV 2 interactions with host microbiome virome communities clotting coagulation issues dysfunctional brainstem vagus nerve signaling ongoing activity of primed immune cells and autoimmunity due to molecular mimicry between pathogen and host proteins The individualized nature of PASC symptoms suggests that different therapeutic approaches may be required to best manage care for specific patients with the diagnosis 