Why do rabies only infect mammals?


Why do rabies only infect mammals?

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Viruses aren’t really alive in the traditional sense, they’re more like landmines with a specific locking mechanism on them that’s designed to specifically attack cells with the same lock.

Rabies, and most other mammalian viruses, have locks that work on mammal cells at mammal body temperatures.

Reptiles and mammals diverged 300 million years ago and in that time our cellular defenses have changed considerably. It’s very difficult to design an inert virus that can unlock two very different types of cells.

The vast majority of viruses only infect bacteria. You are covered in bacteria and viruses that never evolved to infect you. Rabies did evolve to infect you and it does so in a way that allows it to infect many/most/all mammals by exploiting traits shared by all its targets. You could say it has the mammal master key.