is this a virus and how do I get rid of it?

Excerpted from Effective defenses against malware and other threats - Apple Community:

Beware spontaneously appearing, unsolicited popups demanding immediate action. Think before you click.

• ...
• If you encounter a website, popup, text message, email, or phone call alleging your Mac is infested with some ick or that you need to take immediate action lest dire circumstances ensue, it is 100% fraudulent. Ignore it. Read Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams - Apple Support.
• The same goes for website Notifications — attention-getting banners that appear at the top right corner of your screen. Safari gives you a great degree of control over them: Customize website notifications in Safari on Mac. Most of those Notifications are simply annoying, but some are intended to frighten and deceive you into installing something nefarious.

... how do I get rid of it?

Follow the instructions for customizing website Notifications above. Choose "Deny" for all websites except those for which you require Notifications to be sent. Most Notifications are just annoying, but some (like your example) are intended to cause unjustified concern. Clicking the banner will load a webpage that will attempt to deceive you into installing something nefarious. I recommend the best practice is to reflexively deny any and all such requests: Just say no.

No. It looks like a website pop up.