Thrush is a yeast infection caused by a fungus called Candida albicans. Both men and women can get thrush, though it is more often associated with women.The medical term for thrush is candidiasis.ntroduction. Thrush is a yeast infection caused by a fungus called Candida albicans. Both men and women can get thrush, though it is more often associated with women. The medical term for thrush is candidiasis.