What is the difference between being asymptomatic and presymptomatic in COVID-19 coronavirus patients? Asymptomatic means you’re not showing any symptoms of illness. If you have tested positive for Covid, but aren’t showing signs of the illness, then you might be an “asymptomatic carrier” of the coronavirus, and could possibly infect others without knowing it. According to studies in the Washington nursing home and also in China, most (perhaps 3 of 4) asymptomatic patients turn out to be “presymptomatic”. This means the patients ultimately DO show signs of the illness, but the symptoms come some days AFTER the patient tested positive. Most often we think of symptoms first, then testing positive on a nose-throat swab test. Presymptomatic people are the other way around – they test positive first, then later show symptoms. In a China study of 94 patients, they estimated infectiousness started 2 to 3 days ahead of symptom onset, and reached its peak about 14 hours before symptoms began to show. They estimated about 44% of transmission to others occurs before symptoms come on. Read this April 13, 2020 article from NPR discussing how the coronavirus is spread from person to person.