It most likely is a scam. It's very unlikely that Android would get a virus in the first place, look up sandboxed OS and Android, and many of the shadier devs, let's not forget Android is open platform, use scare tactics to get from app views and downloads for ad dollars. Often devs will even put out a game or other miscellaneous app and push these anti virus, battery saver, total defense, memory saver apps that they've developed and many of them do more harm than good. Even worse some are phishing apps that either want your social networking information, your contacts, or in worst case your identity. Anyway uninstall whatever is telling you this and move on. I wouldn't put any anti virus app on the device because of the low possibility of getting such an infection. 9 times out of 10 of your phone is acting up there's a nefarious app behind it that was installed with too many permissions. Does a photo app really need to make calls? Do games really need to view your pictures and access your texts?
Simple rules to droid by, install nothing under 3.5 stars, nothing that has as many 1 star reviews as 5 star, nothing that has less than 100k installs, and absolutely nothing that you haven't read at least five 1 star reviews on. The low rates reviews will tell you the problems with the apps, the others can be faked.