How many members of AC DC are still alive?

I'm curious, how many members of the iconic rock band AC/DC are still actively performing and alive today? With a long and storied history, it's fascinating to know how many of the original lineup or later additions to the group are still with us, rocking out on stage or otherwise keeping the spirit of AC/DC alive. It's always a treat to see the band members perform, so I'm eager to learn the current status of their membership.