Android Question

Hi. I always charge my galaxy S4 overnight then it usually lasts till about 9pm. But the last 2 days its gone by around 2pm, but I am not using it more, could it have a virus?
Probably not a virus or malware. Unless you've been installing apps from dodgy sites it's extremely unlikely in fact.

However, it could be that one of your apps has had a bad update. This includes Google apps, such as Google Play Store or Play Services, which update silently whether you want them to or not. If you can find out which app is responsible then uninstalling it will fix it if it's one you don't need, or maybe even just stopping it or clearing it's cache will be enough. There was one Google problem last year which caused location services to use a lot of power, in which case turning location off worked until a fix was released.

You could try installing GSam Battery Monitor, let the phone run through a full cycle then see what is using the power. Once you've identified the cause you can work out what you can do about it.

Of course the first thing I'd do is reboot the phone - sometimes that's enough.