iPhone Touch Disease, or Touch IC disease as it is so-called is a failure of on the mainboard of the iPhone (affecting iPhone 6 Plus models especcially) that casues a degradation and eventual failure of the iPhone's touchscreen response.
Essentially you will find that over time as you attempt to interact with the iPhone's touchscreen it will become more and more difficult to activate the controls and eventually nothing will hapen when you touch or swipe.
Some are calling this problem (which Apple has acknowledged exists) a defect. However Apple's website indicates that the failure is a result of repeated drops, knocks and/or other stresses experienced by the iPhone. They are neither covering failure under warranty nor repairing the damage -- leaving affected users to their own devices to find a solution from a third party repair shop.
The cause of the problem consists of the failure of 2 integrated circuits on the iPhone mainboard - namely the U2402 & U2401 chips which require replacement in order to provide a solution.
A distorted grey band may show intermittently at the top of the display.
This distinctive grey band is usually a tell-tale sign that your iPhone is suffering from the mainboard surface-mounted component failure known as Touch Disease, Touch IC Disease or Touch IC Failure.