Sharing air with someone while neither of you is wearing a mask. Families can be breath bonded. Co-workers can be breath-bonded. Lovers can be breath-bonded.
In the context of harm reduction, one would limit the number of people with whom one breath bonds to minimize community spread.
"I tell ya, Pat. I never thought I would need to consider how my breath might impact the health of another person, but here we are. I'm being careful about breath bonding with folks."