There are biological factors that put young women at high risk of HIV infection. (Photo/ Flickr/ Matthew Birch)

Bacteria Could Be Behind The Spread of HIV/AIDS, Who Knew?

YOUNG women bear a disproportionate burden of HIV in sub-Saharan Africa – and South Africa has a particular challenge. In some parts of the country more than 36% of people are HIV positive.

Three studies conducted by the Centre for the AIDS Programme of Research in South Africa (Caprisa) in rural and urban sub-districts of the KwaZulu-Natal province provide new insights into the engine that drives HIV transmission in the country. They also reveal a new way to tackle the problem of HIV.

The first study interrogated sexual relationships between older men and younger women. This data showed that adolescent girls and young women were contracting HIV from their partners, who were on average eight years older.

This form of cross-generational sex is not new, but has recently enjoyed a resurgence in popular culture as the “blesser” lifestyle – older men who shower young women with money and gifts, such as clothes, cars, apartments and overseas trips in exchange for sex.

These older men were simultaneously in sexual relationships with women – of similar ages to the men – who have HIV prevalence rates exceeding 60%. This is where the “cycle of transmission” became apparent.


Older women, who are HIV positive, are in relationships with men the same age as themselves. These men, who are mostly unaware of their HIV status, are then also sleeping with younger women. The younger women will then contract HIV and when they grow up they will become the source of infection for men in the same age group as them. This perpetuates the cycle.

In addition to this “cycle of transmission”, our other two studies revealed biological factors that put young women at high risk of HIV infection. First, we analysed vaginal bacteria.

Lactobacillus bacteria, which is naturally present in the vagina. (Photo/ Flickr/ Sage_Anne)

Lactobacillus bacteria, which is naturally present in the vagina. (Photo/ Flickr/ Sage_Anne)

Women who had an abundance of a naturally present bacterium (Prevotella bivia) had a 13-fold increased risk of acquiring HIV.

Overgrowth of the bacteria resulted in a protein called lipopolysaccaride being released which increased genital inflammation 20-fold. This genital inflammation increases vulnerability to HIV infection and places young women with excess Prevotella bivia at greater risk of becoming HIV positive.


The third study also looked at genital bacteria in women. Here we wanted to gain a better understanding of the efficacy of tenofovir gel being used as a pre-exposure prophylaxis (PrEP). That’s using anti-retroviral drugs as a prevention against contracting HIV.

It showed that tenofovir gel was effective in three out of five women who had a dominant presence of a bacteria called lactobacillus. Lactobacillus bacteria is naturally present in the vagina and hlps maintain an acidic pH. This is beneficial as it maintains a “healthy” vaginal environment.

Women with low levels of this bacteria ended up having a reduced amount of tenofovir present, so PrEP was not as effective.

Our studies show that treatment is key but you need additional measures. Circumcision in young men will reduce their risk of contracting HIV but there may still be some transmission. Young girls also need to be protected with pre-exposure prophylaxis.

In total, test and treat initiatives with circumcision and PrEPs are a combination that can break the patterns of HIV transmission. But the critical issue is that we cannot adopt an ostrich approach to older men sleeping with younger women. We need a new set of community norms.

A slightly longer version of this article was first published on The Conversation.

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