BV is the most common genitourinary tract infection to affect women in their reproductive years² although around half of those affected may be asymptomatic.¹¹ The mechanisms that cause BV are not yet fully understood,¹ but G vaginalis has been identified as a common pathogen.¹²

Other bacteria likely to increase in numbers include Atopobium vaginae, Mobiluncus spp, Bacteroides spp, and Prevotella spp, which can co-exist in a "thick vaginal multi-species biofilm".² Vaginal conditions change, becoming less acidic, rising above pH 4.5.⁵

Recurrent BV may stem from the pathogenic bacteria not being completely eradicated, very likely because of the protective biofilm, or the benign Lactobacilli being unable to re-establish themselves and restore the homeostasis. Another factor may be re-infection from partners.¹³