Most people with COVID-19 are contagious from about 1 to 2 days before symptoms start until around 8 to 10 days after they begin, with the highest risk of passing the virus on in the 2 days before and the first 3 days after symptom onset. This is when the virus is usually present in greater amounts in the nose and throat.
In healthy adults, contagiousness tends to drop sharply after the first week, and most stop spreading the virus by about day 7 to 10, especially if they are vaccinated. People with weakened immune systems or very severe COVID-19 can remain contagious for much longer, sometimes for several weeks, and often need personalized medical advice and sometimes repeat testing to know when it is safer to be around others.
Because the virus spreads easily in the early days of infection, anyone with suspected or confirmed COVID-19 should stay home, avoid close contact with others, keep rooms well ventilated and consider wearing a well-fitted mask around household members.