A vaginal yeast infection, also known as candidiasis, is a fungal infection. When the balance of bacteria and yeast cells in the vagina changes, the yeast cells can multiply and cause an infection. 3 out of 4 women can get a yeast infection at some point in their life. The yeast infection is not considered to be transmitted by sexual intercourse, but the risk of developing an infection is higher because bacteria can be introduced during sexual activity. Earlier diagnosis and treatment can cure yeast infections.