False virus warnings are called push notifications and will occur if you accidentally give scammers permission to push notifications to your computer. These generally appear in the bottom-right corner of your computer screen.
In all probably you do not really have a virus, instead the scammers are hoping to earn commissions from selling legitimate McAfee or Norton anti virus software.
This video shows how to easily block McAfee and other false virus push notifications.
Take the opportunity to connect and share this video with your friends and family if you find it useful.