UTI is to a high extent auto-infectious: we infect ourselves with our own stool. It is more common in women and children as they have shorter urethra nearer to the anus. E-coli is an opportunistic bacterium: sometimes it’s our ally, (in Vietnamese Lợi khuẩn), helping us with our digestion, but it can also be an enemy (Vi khuẩn), causing disease if in the wrong place of the body.