[alexander_busek]

Just one question: Are there any other mammalian species plagued by this (or similar) viruses, against which an immunity could be developed by kissing?

I had always thought that it derived from the practice in most primitive cultures (lacking Cuisinarts) of feeding babies and invalids by pre-chewing the food and then transferring it to their mouths.

Regards,

[Dysart]

Interesting question. And you would think the answer would be yes, but I don’t have any specific info. Good second point re pre-chewing conferring immunity. Same mechanism.