Well I can read:
COVID-19 (coronavirus disease 2019) is a respiratory illness caused by the SARS-CoV-2 virus. It is very contagious, and spreads quickly. Most people with COVID-19 have mild respiratory symptoms that feel much like a cold or flu. But it can be much more serious for older adults, people with...
www.health.harvard.edu
"Most people with coronavirus who have symptoms will no longer be contagious by 10 days after symptoms resolve."
...and I can do math:
"The time from exposure to symptom onset (known as the incubation period) is thought to be three to 14 days, though symptoms typically appear within four or five days after exposure."
Add that up and you get a month? That doesn't take an epidemiologist.