that is not how HIV/AIDS is spread.

You could potentially get herpes from it, but idk how long the virus lives on porous material like wood exposed to the elements. Covid for instance lasts 4 days on wood, but only 1 on cardboard. It lives much longer on, say, plastic, than on clothing.

I'd be much more worried about toxic chemicals because outdoor furniture almost certainly uses treated wood. And if it's pre-i-think-80s treated wood it's even worse.