Touch

According to the Second Doctor, touch was one of the five senses of human beings. (TV: The Evil of the Daleks)

Victims of the Empty Child plague transmitted their affliction with a touch. (TV: The Empty Child) Similarily, the new humans created by the Sisters of Plenitude transmitted all the diseases they carried with a touch, proving fatal for those they came into contact with. (TV: New Earth)

The Abzorbaloff absorbed his victims by touching them. While disguised as "Victor Kennedy", he warned people against touching him, claiming to suffer from eczema. Whilst in the process of being absorbed, Ursula warned Elton Pope not to touch her. (TV: Love & Monsters)

Mother Doomfinger of the Carrionites demonstrated the ability to kill with a "touch of the heart", placing her finger on the chests of her victims. (TV: The Shakespeare Code)