What's an iPhone Touch disease ?

Actually its a design defect to do with iPhone's 6 series and the chips controlling the touch controller of the screen. Apparently iPhones affected by it end up with a flashing grey bar and being unable to use the touch screen. Apple is currently being sued for it.

The actual cause is suspected to be the way Apple changed the the way the touch control chips are mounted to the board and also Apple removed a metal shielding plate too. With the way phones tend to subtly bend and and a combination of heat the exposed chips end up coming loose. Theres a decent video here explaining it and how people fix it.