The caster whispers in his closed fist and then gently opens his palm to blow from it some kind of dust. The powder travels to the target and enters his/her body. After that happens and that players turn has started he/she will take 2d4 poison damage for 3 turns or half of that on a succesfull constitution saving throw. After that happens the virus will transmit to each target that stands 5ft from the one originally inflicted if the poison effect still applies. When one is inflicted the same thing happens to him/her and if someone already inflicted by the virus is imposed to it again the virus will be reapplied and so will be the turns of the poison remaining.
This willbecome a domino effect that if used correctly could make for an interesting challenge. You could also not say that someone has a virus that is transmitable but hint it's transmisive nature such as it's dust form moving from someone to another.
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