A combination of biological, social, cultural and economic factors contribute to the rise of female infection.  In particular, prevalent gender inequalities constrain the capacity of women to assert power over their own lives and to control the circumstances that increase their vulnerability to infection, particularly in the context of sexual relationships.

a) Biological factors - It is believed that women may be biologically more susceptible to HIV infection from heterosexual sex than men.  Because the female genital tract has a greater exposed surface area than the male genital tract, women may be prone to greater per-exposure risk of infection. Male to female transmission is estimated to be twice as likely as female to male in a single act of vaginal intercourse.

b) Social and cultural factors - Social and cultural norms contribute to the unequal status of women in society and this contributes to the spread of disease. Particularly in the developing world, women are often denied the power to make the decisions about their sexual relationships that may lower their risk of HIV infection.  Social norms restrict women’s ability to negotiate sex with a condom, demand fidelity in a relationship or seek information about protection, treatment or health care.

The unequal power balance between men and women puts women at a greater risk.  For example, social norms may dictate that women remain monogamous, while men may be allowed and even encouraged to engage in sex with multiple partners. Fear of violence, rejection and abandonment are additional factors that contribute to women’s vulnerability.

c) Economic factors - Poverty and the reliance on men for economic support compound women’s risk of infection.  The lack of productive resources may force women to engage in unsafe sex or may force them to exchange sex for money or material favors as a means of survival or to support their children. The fact that women are often financially and materially dependent on men makes it difficult or impossible for them to take control of their sexual relationships.