A bladder infection, also called cystitis, is a type of urinary tract infection.
Bacteria usually cause the infection.
Rarely a virus may cause it. A bladder infection occurs when bacteria travel up the urethra and into the bladder. Women are more likely to have bladder infections than men because their urethra is shorter. The short urethra makes it easier for bacteria from the anus or genital area to reach the bladder. This can happen during such activities as wiping or sexual intercourse.