It's probably (most likely) NOT a virus, unless you've installed apps from outside the Google App store.
That said, an app may be misbehaving and causing wakelocks (keeps the phone from going into low power mode). Uninstall any apps you've recently downloaded. If that doesn't help, do a factory reset and install your apps one at a time until you determine that all is good, OR you find the most recent app that's causing the issie.