Definitely not short circuit or it would squeal/no sound. This is likely a grounding problem.
1. Make sure the equipment you are using is grounded (three-prong plug).
2. Clean your jack socket with Electrical contact cleaner
3. Make sure the shielding inside your guitar is still grounded
4. If the hum stops when you touch the strings this is likely a bridge ground problem (the ground wire attached to your bridge got disconnected)

Fluorescent lights, dimmer switches, computer screens are a source of hum if they are close by, if hum changes when you move, it may come from there.
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