That's how vaccines work. A low dose of an attenuated virus or bacteria stimulates an immune response.
I worked in immunology research for 18 years - specifically researching the herpes class virus. Trust me, you can't get herpes from a dirty touchscreen or keyboard.
I don't think I'm going out on a limb with this one when I say that I am pretty confident that you can't get diabetes from a dirty keyboard or touchscreen either.
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