x1 gives/exchanges/spreads contagion x2 to x3 via means x4; x1 infects x3 with x2.
x2 is a contagion in the sense of prejume1. x3 may be an individual or a population, or even an object which itself cannot be a long-term host of x2. This word is a brapagjvo in part from "prejume". The infection need not be sustained/successful (from the standpoint of the would-be contagion x2); the infection need not be noticeable or cause adverse effects (use this word in conjunction with "bilma" for that) - this is purely about the act of exchanging. Technically, lo prejume cannot really prejumydu'a something else - English conflates "infect" as in "Harry (a person) infected Ron (another person) with the flu" with "infect" as in "the flu infected Ron"/"Ron was infected by the flu" (where the point of origination is not of focus, merely the fact that the flu is spreading throughout Ron's body).