Does infect damage deal regular damage to players or only poison counters?

Infect is a keyword ability defined in CR 702.90. When a source with infect deals damage to a player, that damage is dealt in the form of poison counters rather than loss of life. Each 1 point of damage translates to 1 poison counter placed on that player. Regular damage to life total does not occur at all.

When a source with infect deals damage to a creature, it works differently: instead of damage counters, it deals damage in the form of -1/-1 counters (CR 702.90b). So infect replaces both the normal player damage and the normal creature damage with these alternative effects.

A player who accumulates 10 or more poison counters loses the game immediately as a state-based action (CR 104.3c, 722.1). This is entirely separate from their life total — a player at 20 life with 10 poison counters still loses.

Example: Your opponent attacks you with a 3/3 creature with infect. It deals 3 damage to you — but instead of losing 3 life, you receive 3 poison counters. Your life total remains unchanged. If you later accumulate 7 more poison counters from other sources, you lose the game.

Note that effects that prevent or redirect damage still work normally against infect sources (CR 702.90c). Infect only changes how the damage is applied once it resolves, not whether damage is dealt.