[kikito]

I still did not found the else if...
From ricardo178, but EDITED a bit.

pawn Code:

public OnPlayerDeath(playerid, killerid, reason)
{
    if(gTeam[killerid] == TEAM_HUMAN)//If the killer id is human
    {
        gTeam[playerid] = TEAM_ZOMBIE; // will for for zombie
        GameTextForPlayer(playerid,"~r~Infected",3000,4);
    }
    else if(gTeam[killerid] == TEAM_ZOMBIE)//If killerid is zombie
    {
        gTeam[killerid] = TEAM_HUMAN;//will get moved for human
        GameTextForPlayer(killerid,"~r~Cured",3000,4);
    }
    return 1;
}

Test this one, should work