In a shocking warning Staffordshire Police are telling people if they spot Joshua Smith they must not touch him.
The 27-year-old, from Stone, is believed to have ingested a harmful substance.
Physical contact could lead to, “substance transfer”, officers explained.
Search aircraft and specialist teams have been scouring the countryside for Smith, who comes from the Aston area.
He was picked up on CCTV at 8.35am, last Tuesday (October 25), at the cross roads of Lichfield Road and Uttoxeter Road.
But it is not known in which direction he went from there.
Despite the poor quality of the CCTV images the police are certain they show the missing man.
Smith is described as white, thinly built, 5ft 10ins-tall and blue eyed.
His light hair is longer on top than on the sides of his head.
He has a bushy beard and wears glasses.
When last seen he was wearing a black three-quarter length coat, black work boots and carrying a mustard backpack.
Detective Inspector Alan Lyford, said: “We are becoming increasingly concerned for Joshua’s wellbeing and are doing everything we can to find him.”
He appealed to everyone who sees their missing person appeal to pass it on to everyone they could.
The police search is currently covering a wide area, taking in Stone, Stoke-on-Trent and the Roaches.
Wide search area
So far they have discovered nothing to help them narrow down the target area.
Anyone who does see Smith is urged to ring ‘999’ immediately and call for emergency medical support for him.
People who have information about his whereabouts are asked to ring ‘101’, quoting incident number 639, of October 25.