Regarding coronavirus, is there an amount of time from the end of symptoms that someone should quarantine? is there a risk of transmitting or coming back after symptoms have ended?

Probably a week : In my opinion, if you are positive for COVID-19 and your symptoms have resolved, you shouldn't be considered contagious after a week from the resolution of your symptoms. However because a lot is still unknown about this virus, you should still stay at home and avoid public places. If this cannot be avoided, you should defend yourself with a mask and gloves and wash hands frequently. Stay safe!

Per Harvard Health:: “Most people with coronavirus who have symptoms will no longer be contagious by 10 days after symptoms resolve. People who test positive for the virus but never develop symptoms over the following 10 days after testing are probably no longer contagious, but again there are documented exceptions. So some experts are still recommending 14 days of isolation. “REF: https://www.health.harvard.edu/disea