Note that the word 'infection' has a stigma to it, but I don't mean it to be necessarily a bad thing. I will use 'disease' to mean 'infection with bad consequences'.

There's also the word "contagion" to consider.

The dictionary entry for that includes:

the spreading of an emotional or mental state among a number of people: the contagion of mirth.

It explicitly includes culture and has weaker implications of being deleterious. I think what we really need is the terminology of generalised epidemiology, though.