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Raymond Johnson of St Louis, Missouri, says that the poorly washed hands of
food service workers lead to an estimated 12.5 million cases of food borne
illnesses in the US each year. Medical workers cross-infect patients if they do
not wash between treatments. Johnson suggests such workers should wash with a
garish blue or green soap, in front of a colour video camera which digitises the
image and conducts a pixel-by-pixel analysis to work out whether soap has been
applied all over the hands (WO 98/36258). If too large a proportion remains
unwashed, the camera sounds a warning that the employee’s hands may still be
dirty—so they have to wash again.