First of all, you can't look at this movie in terms of realism, it's just a big psychadelic dream. Yes, we all know computer viruses and human viruses can't be transmitted to one another; but it's also not the point of this movie. This movie has to be looked upon as pure fantasy, not as a study of possible future reality. Hell, the solid red, green, and yellow color schemes should clue you in that this is more like 60's psychadelic dreams. Other clues that this is fantasy is that Rosetta talks to her clones, Ruby, Olive, and Marine through a microwave oven!
One great line in the movie that really got me rolling on the floor was when Olive tells Marine that a virus that she just eradicated was from an attachment, and Marine responds that "Rosetta was right attachments are dangerous". Of course, this was double entendre, one meaning of the word "attachment" meant email attachments, while the other one meant relationships. If you didn't understand this movie the first time, then you owe it to yourself to watch it again to catch all of these little pokes at modern life.