Epidemiology of HIV in Africa

Discuss the prevalence of HIV in Sub-Saharan Africa.

With all of the publicity around AIDS in Africa, whilst the numbers are certainly shattering, it was very surprising to learn that only 2.8% (24 million people) of the total population of Africa’s 850 million people, are HIV positive [1].  Most of these live n Sub-Saharan Africa, where 23.5 million people were estimated to have HIV in 2011 [1]. This represents almost 70% of the worldwide burden of disease (estimated to be 34 million people) [2, page 8].

In Epidemiology, the term “prevalence” is defined as the number of people currently living with a particular disease, whilst “incidence” is defined as the number of new infections occurring in a given timeframe [3].  The Centers for Disease Control and Prevention (CDC) define an epidemic as “the occurrence of more cases of disease than would normally be expected in a specific place or group of people over a given period of time” [4].  The HIV-AIDS epidemic is divided into four defined categories, being:
1.  Generalised – where HIV prevalence in the general population of a given country, region or location is equal to, or more than, 1%;
2.  Concentrated – where the HIV prevalence in the general population is less than 1%, but exceeds 5% in specific high risk groups, such as injecting drug users;
3.  Low level – insignificant prevalence in any group;
4.  The number of people who have died from AIDS is also an important consideration, as a significant number of AIDS deaths may alter the prevalence figures.

The World Bank provide an interactive table / graph / map on their website [5], which demonstrates the difference in prevalence rates in 15-49 year olds in different countries.  This clearly shows marked differences in HIV prevalence between countries on the African continent for 2011.  Swaziland appears to have the highest rate at 26%, followed by Botswana (23.4%), Lesotho (23.3%) and South Africa (17.3%). These highest prevalence countries are all in Southern, Sub-Saharan Africa.  In contrast, some African countries have much lower prevalence, for example Angola (2.1%), and the northern nations of Burkina Faso (1.1%) and Tunisia (0.1%) [5].

Prevalence rates do not necessarily demonstrate the affliction of disease when translated into numbers, or global burden.  For example, because Nigeria is a populous country of 162.5 million people [6], their prevalence rate of 3.7% amongst 15 to 49 year olds [5] equals 3.3 million, which translates to 10% of the world’s total HIV positive population [7].

Approximately 10% (3.4 million) of all HIV cases worldwide are estimated to be children under the age of 15, and it is also estimated that around 16 million children worldwide have lost at least one parent to AIDS related death [8].  Consistent with the other figures discussed above, most of these children live in Sub-Saharan Africa, and 90% of HIV positive children became infected via Maternal to Child Transmission either peri-natally (before or during birth), or via breastfeeding [8].

Because most HIV transmission in Sub-Saharan Africa occurs during unprotected heterosexual intercourse, and because women are much more vulnerable to infection via heterosexual transmission, women are much more likely to become infected with HIV via this exposure route [9].  In 1985 HIV prevalence in Sub-Saharan Africa was approximately equal between men and women [9], but due to the vulnerability of women to infection, 58% of all HIV positive people in this region are now women [2].

There are many other sub-populations with varying prevalence rates, for example sex workers, injecting drug users, men who have sex with men, and prisoners, who are all vulnerable to HIV transmission for differing reasons [19] which go beyond the scope of this assignment.

Prevalence rates are not a static phenomenon, and they change over time, and within populations.  For example, in South Africa 5.6 million people were estimated to be HIV positive in 2011, which is “the highest number of people for any country” [16].  South Africa has conducted annual ante-natal HIV seroprevalence surveys since 1990, at which time 0.8% of pregnant women were estimated to be HIV positive.  This statistic rose steadily for the next 15 years, and in 2005 30.2% of pregnant women were estimated to be HIV positive [17].  Since this time, HIV seroprevalence in pregnant women in South Africa has remained stable [18].

It is very difficult to compose a concise argument as to what factors influence the different prevalence rates of HIV between populations geographically.  According to the UNAIDS Report on the Global AIDS Epidemic 2012, “behaviour change is helping to prevent sexual transmission in generalized epidemics” [10, page 16].  Across Sub-Saharan Africa, efforts are being made to influence sexual behaviours in young people.  For example the Global Dialogues project, a script writing contest held across the continent, in which winning short films addressing issues in HIV-AIDS are broadcast widely to African television stations, and used as education resources in a wide variety of community contexts.  The narratives are studied “to understand how youths perceive HIV/AIDS and related social phenomena”  [11].  Couples Voluntary Counselling and Testing (CVCT) has also been identified as “the only prevention program proven to reduce HIV incidence in the largest risk group in the world, African couples” [12].

HIV infection rates are highest in poorer populations and the interplay between HIV and poverty is complicated and not easily understood or articulated, with low literacy, gender inequality, early age marriage and child labour being just some of the issues increasing HIV infection risk [13].

Other social factors related to high HIV transmission rates include sexual violence, high sexually transmitted infection (STI) rates, low rates of male circumcision, population transience and mass movement into cities [14].  Concurrent sexual partnerships have been defined as “situations in which an individual has overlapping sexual relationships with more than one person”, and are reportedly much more common in Sub-Saharan Africa [15], however the connection between concurrent partnerships and HIV transmission rates remain hotly debated [15].  There are also some possible physiological causes for higher rates of HIV transmission, including transmissibility of different virus sub types, genetic factors, and co-infection with certain helminths [14].

Political leadership at global, national and local levels is considered a key influence in the outcome of HIV prevention programs [20].  Weak economies and political unrest are considered significant barriers to successful prevention programs in many places, but South Africa and Botswana are two examples of countries showing committed leadership with improved outcomes [7].

1.  http://www.unaids.org/en/resources/campaigns/20121120_globalreport2012/epislides/ (Slide 4/12)
2.  http://www.unaids.org/en/media/unaids/contentassets/documents/epidemiology/2012/gr2012/2012_FS_regional_ssa_en.pdf
3.  http://www.avert.org/aids-statistics.htm
4.  http://www.cdc.gov/excite/classroom/intro_epi.htm (See Disease Transmission)
5.  http://data.worldbank.org/indicator/SH.DYN.AIDS.ZS/countries/all?display=default
6.  http://data.worldbank.org/indicator/SP.POP.TOTL
7.  http://www.avert.org/aids-hiv-africa.htm
8.  http://www.avert.org/children.htm
9.  http://www.avert.org/women-hiv-aids.htm
10.  http://www.unaids.org/en/media/unaids/contentassets/documents/epidemiology/2012/gr2012/20121120_UNAIDS_Global_Report_2012_with_annexes_en.pdf
11.  http://globaldialogues.org/the-issues/hivaids/#.UUhYB1fV5Fs
12.  http://www.rzhrg.org/couples.html
13.  http://www.un.org/wcm/content/site/chronicle/home/archive/issues2011/hivaidsthefourthdecade/impactofhivaidsoneducationandpoverty
14.  http://www.avert.org/aids-africa-questions.htm
15.  http://www.aidsmap.com/Concurrent-sexual-partnerships-and-the-spread-of-HIV-the-evidence-is-limited/page/1437223/
16.  http://www.avert.org/aidssouthafrica.htm
17.  http://www.hivsa.com/static/hiv-aids-in-south-africa
18.  http://www.avert.org/south-africa-hiv-aids-statistics.htm
19.  http://www.avert.org/hiv-aids-vulnerable-groups.htm
20.  http://www.ncbi.nlm.nih.gov/pubmed/21161769

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