viral scan needed?

No. the Mac is generally not subject to arbitrary attack. So-called Anti-Virus scanners just makes a big show of checking for stuff that is not going to attack your Mac, and makes it unstable while doing so.

However, the professional criminals on the Internet ARE out to get you (especially your private information) and will stop at nothing to get you to click on their links and install their malware.

If you think that you might have adware on your Mac, update to the most recent version of OS X El Capitan. If your Mac already has the most recent version of El Capitan, restart it. El Capitan removes adware only at login.

from:

Stop pop-up ads in Safari - Apple Support

http://www.apple.com/osx/what-is/security/

.

belinda118 wrote:

does the MacBook need a viral scan?

No, that would be pointless, and depending on the product being offered it will likely cause trouble. If you encountered a web page suggesting that you do so, it's a common scam that you should summarily ignore. Read Phony "tech support" / "ransomware" popups and web pages.

For a more in depth discussion read Effective defenses against malware and other threats.