(introduction...)

Women in the developing world are at higher risk of HIV infection than their male counterparts for a number of reasons, biological and sociological.

Biological factors

The rate of transmission of HIV from male to female is two to three times higher than that from female to male^27,28. The Langerhans' cells of the cervix may provide a portal of entry for HIV and it has been suggested that some HIV serotypes may have higher affinity for these, and therefore to be more efficient in heterosexual transmission²⁹.

Vulval and vaginal inflammation or ulceration may facilitate entry of the virus. Sexually transmitted infections (STI) are common in many African countries, where HIV prevalence is also high^30,31,32. Inadequately treated or "silent" chlamydial and other sexually transmitted infections may act as co-factors for HIV infection and transmission^{33,34,35,36,37,38}. Syphilis rates as high as 30% have been described in antenatal women^39,40 and 4.2% of women in a population based study in the United Republic of Tanzania reported a history of genital ulceration⁴¹, which has been well established as a co-factor for HIV acquisition^42,43,44. In Zimbabwe, women reporting a history of genital ulceration and pelvic inflammatory disease were six times more likely to be HIV-positive⁴⁵. Improved STI treatment in a randomized controlled trial in the United Republic of Tanzania was shown to reduce the rate of new HIV infections⁴⁶. Other non-sexually transmitted cervical lesions, such as schistosomiasis, may also facilitate HIV infection⁴⁷. Although the evidence is still inconclusive, associations between oral and injectable contraceptive use and increased HIV risk have been reported^48,49.

Socio-cultural factors

Women are essentially at more risk in cultures and communities that remove their control over their own bodies. Women are often blamed incorrectly as the source of HIV infection and carry the dual burden of infection and of caring for infected family members. Gender inequalities, poverty, less access to education and lack of employment opportunities force many women into commercial sex work in order to survive, and this group of women are at very high risk of HIV infection^50,51. Conversely, many more women are monogamous, but are at high risk due to the sexual behaviour of their male partner. Traditional practices and customs such as "dry sex" practices, vaginal douching with non antiseptic compounds, female circumcision and "widow cleansing" may all have an effect on increasing women's risk of HIV infection^{51,52,53,54,55,56,57}. Despite their high risk of infection, cultural practices and pressures often prevent women from taking the necessary precautions to guard against infection. Use of male condoms is low in many developing countries. The desire and the societal pressure to reproduce make it difficult for women to practice protected sex. Young women are at highest risk of infections in developing countries, many of them at the beginning of their reproductive lives. Even after a diagnosis of HIV infection, most women will not change their reproductive choices^58,59. There are no methods available for women to use to prevent HIV transmission, independent of the male partner, with the possible exception of the female condom^60,61. Female barrier methods remain expensive or unavailable in most developing countries, where male resistance to condom use is common, although the recent introduction of social marketing of the female condom in some southern African countries has demonstrated that there is considerable demand.