Asymptomatic or pre-symptomatic Infection: Individuals who test positive for SARS-CoV-2 by virologic testing using a molecular diagnostic (e.g., polymerase chain reaction) or antigen test, but have no symptoms.
Mild illness: individuals who have any of the various signs and symptoms of COVID-19 (e.g., fever, cough, sore throat, malaise, headache, muscle pain) without shortness of breath, dyspnoea, or abnormal chest imaging.
Moderate illness: Individuals who have evidence of lower respiratory disease by clinical assessment or imaging and saturation of oxygen (Sp02) >94% on room air at sea level.
Severe illness: Individuals who have respiratory frequency >30 breaths per minute, Sp02 <94% on room air at sea level, ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (Pa02/Fi02) <300 mmHg, or lung infiltrates >50%.
Critical illness: individuals who have respiratory failure, septic shock, and/or multiple organ dysfunction.
Molnupiravir can swap between two forms (tautomers), one of which mimics cytidine (C) and the other of which mimics uridine (U). NHC-TP is not recognized as an error by the virus’ proofreading exonuclease enzymes, which can replace mutated nucleotides with corrected versions. When the viral RNA polymerase attempts to copy RNA containing molnupiravir, it sometimes interprets it as C and sometimes as U. This causes more mutations in all downstream copies than the virus can survive, an effect called viral error catastrophe or lethal mutagenesis.
