Plenary: Global Health Forum National University of Ireland, Maynooth

1. Why 'Sexual Networks': The importance of social structure and scale in a sexually transmitted epidemicProfessor Robert Thornton, AnthropologyUniversity of the Witwatersrand, Johannesburg Plenary: Global Health ForumNational University of Ireland, Maynooth This talk is based on the book:Unimagined Community: Sex, Networks, and AIDS in Uganda and South AfricaCalifornia Series in Public Anthropology, 20; University of California Press

2. Sex, networks and AIDS in Uganda and South Africa Robert J. Thornton Unimagined Community: Sex, Networks, and AIDS in Uganda and South Africa California Series in Public Anthropology, 20 304 pages, 6 x 9 inches, 7 b/w photographs, 13 line illustrations. September 2008, Available worldwide

3. Me . . . • Why do I presume to talk about sex in Africa? “I did not want to study AIDS, but … I could not avoid it. Anthropology has been called the study of mankind in context. HIV/AIDS is now part of that context. … It touches on the deepest of human concerns: sex, health, death, kinship, family, language, and culture. … My concern with HIV/AIDS is an anthropological concern … [that] departs significantly from standard epidemiological, public health, medical, and sociological perspectives and methods.” [p. xvii]

4. The Kamondo family album, Mbarara, Uganda—1970s to 2003 1979 2003

5. And later: Tanzania, South Africa

6. The book • Changes in individual ‘behaviour’ may have little effect on the HIV epidemic ( e.g South Africa) • I examine social structural issues, including what I call ‘sexual networks’ • ‘Sexual networks’ are social structures, • NOT = ‘multiple concurrent partnerships’ or ‘contact tracing’

7. Why Uganda and South Africa?

8. Why Uganda and South Africa? • South Africa and Uganda exhibit extremely high—and rapidly changing—HIV prevalence • Both have near universal knowledge of HIV/AIDS factors; • Both have high levels of interventions; • yet they are extremely different in the trends of the epidemic.

9. First, Some obvious points • Sex transmits things, including viruses • persons of any ‘gender’ can do sex • HIV is a sexually transmitted virus • Populations are bigger than persons • ‘Epidemics’ are defined at the level of populations • AIDS is an epidemic Therefore…

10. Some not-so-obvious questions • If HIV is sexually transmitted, why is it not always transmitted through sex? • Why do other sexually transmitted infections –such as pregnancy—not behave like HIV? • Why, in southern Africa, is HIV infection so high in women, and is heterosexually transmitted? • What is the relation between a person’s behaviour and the whole population?

11. The first lesson • No system scales up linearly (an engineering principle) • The link between individual motivation and action (such as a sex act), and population-level events (such as epidemics) is not linear, and nor simply arithmetic • The relation between an individual’s behaviour and an epidemic, considered as system, is not linear

12. Second lesson • Epidemics are properties of populations, but • human populations are not random collections of elements (as RCTs assume) • Humans have complex social structures that structure the population (what randomisation attempts to avoid) • Sex is social, and has structure • Populations of humans who have sex have social structures

13. Third lesson • Scale of measurement (size matters): • The focus on individual behaviour excludes social structure, geography, culture, etc. • The focus on ‘epidemic’, as a property of a population, forces us to consider persons as random elements of a population • The only measures we can correlate with this are ‘behaviours’ and economic and political indicators • ‘Behaviours’ are small scale (persons) while economic and political indicators are large scale • What is lacking is attention to structure

14. Lesson 4: An Anthropological approach: beyond behaviour, poverty, & cultural response • The focus on ‘behaviour’ and ‘poverty’ is in part an artefact of method, and of the social ontology we select • We require a more anthropological approach • That goes beyond the ‘cultural response’ to AIDS, and person-centred discussion of sexuality

15. Multiple concurrent partnerships [MCPs] = ‘long term overlapping sexual relationships’ • It has become conventional wisdom that these account for high incidence and prevalence of HIV in southern African countries • But, ‘MCPs’ are simply a fragment of the larger scale 'sexual network', • and the sexual network is ‘structured’ by social and cultural factors • The MCP is simply too small a scale to make sense of a phenomenon that acts at the level of populations.

16. Shifting scales • MCPs are neither population-level, nor individual level, and thus are not appropriate units of analysis. • We need to understand not just the structure of large-scale sexual networks, but also their scale

17. The USAID Report, ‘What Happened in Uganda’, widely circulated, gave the impression that HIV was declining in Uganda simply because of cumulative “behaviour change”

18. Mulago Hospital Nsambya ANC Clinic Rubaga ANC Clinic Incidence Mortality Stoneburner and Low-Beer’s epidemiological model of HIV prevalence change in Uganda (Stoneburner & Low-Beer 2004:717, fig. 3a)

19. A more realistic curve can be easily visualised

20. The power-law model • Most epidemics can be modelled by a version of the the exponential model where f(x) = cekt Where t is time; c, k are constants • This works for most biological systems in which growth depends on the number of previously existing organisms • The power law models systems in which growth depends on the structure of networks f(x) = cta

21. The power-law phenomena • mathematical analysis of networks shows that non-random networks—Internet, social networks, scholarly citations, networks of neurons, and food chains in ecological systems—all show power law patterns. • “Power laws hint that a system may be organizing itself. They arise at phase transitions, when a system is poised at the brink, teetering between order and chaos. They arise in fractals, when an arbitrarily small piece of a complex shape is a microcosm of the whole.” (Strogatz, 2003)

22. Comparison of Ugandan and South African trends, 1992-2002

23. The Ugandan (Kampala) HIV Prevalence trend (1985-2002) using power-law model The Ugandan data suggest a phase transition, or ‘tipping point’ phenomenon

24. The Ugandan trend • Curves of this sort are associated with complex network systems. • In this case, HIV prevalence is a function of the number of sexual contacts (‘links’) between people (network ‘nodes’) in a network of a specific configuration, and • will behave over time in non-linear way that is characteristic of fractal structures. • This is distinctly different from a linear growth that would be seen in simple ‘random diffusion’ models of transmission, or • exponential growth of unbounded biological systems.

25. Fitted power-law curve for Uganda and South Africa, 1985-2002

26. The difference between South African and Uganda • The shape of the two trends (Kampala & 4 cities) for Uganda are virtually identical: specific data points may be in error, but trends are accurate. • In 1992, HIV prevalence in Uganda declines rapidly at first, then tails off slowly without tending towards zero. • The Ugandan trends follow a ‘power law’ curve (a characteristic of all network systems). • The South Africa trend shows a nearly linear increase over the same period (but still fits closely a power-law model).

27. Cultural and structural determinates of network configuration

28. Uganda: the cultural systems • The ABC message: the original ‘ABC’ message originated from a Catholic mission in Tanzania • “Abstain from sex” • “Be faithful to your sexual partner” • “Avoid unprotected sex; always use a [picture of condom in a packet]

29. In Uganda, hard hitting, very direct messages were used at first

30. “behaviour” and kinship were linked

31. The consequences soon became obvious

32. Native categories • Silimu, siriimu, were ‘native categories’ that emerged in Luganda and other indigenous Ugandan languages before HIV was identified in the laboratory • siriimu was ‘translated’ into English as ‘slim’ or ‘slim disease’

33. Sirimu: “The stone that is seen does not break the hoe”

34. The indigenization of AIDS Since AIDS was—probably—already an indigenous category of illness in Uganda • An effective political response was both possible, and occurred as Museveni came to power • The ‘multisectoral’ approach emerged • The existence of a native category helped Ugandans to accept the disease and deal with it effectively in political, social, medical, and cultural terms

35. What happened? • The entire Ugandan sexual network reached a ‘tipping point’ and collapsed • This was due to changes in all relevant factors—behaviour change, mortality, education and communication interventions, effective political leadership, etc.—but could not have happened if the Ugandan network was not shaped the way it was • The Ugandan sexual network is highly clustered, ‘fractal,’ and responded non-linearly to change

36. The southern African sexual network • By contrast with Uganda, in South Africa trends suggest a randomised ‘small world’ network in which all sexually active people are relatively closely connected to all others in a nation-wide (or even sub-continental) sexual network. • There is not yet any significant indication that the trend is levelling off.

37. South Africa • Like Uganda, southern Africans (South Africa, Swaziland, Lesotho, southern Mozambique, Zimbabwe, Botswana) share native categories of disease and illness • AIDS and HIV is not included, and is considered to be foreign • Local medical models emphasize the importance of flows of ‘sexual substance’

38. Jacob Zuma’s shower

39. Jacob Zuma’s shower

40. South African Indigenous cultural models

41. South Africa: Indigenous models of the body emphasize flow of sexual fluids

42. The social determinants of the structure of sexual networks • Degrees of social differentiation • Tightness of social and cultural boundaries • Marital patterns • Age of sexual debut • Clan and kinship organisation • Importance of traditional systems of political organization (chiefs, kings) • Family property and land tenure regimes • Degrees of mobility • Urbanisation

43. South Africa • The South(ern) African sexual network is a robust, extensive, Internet-like network that is highly efficient at transmitting HIV • It is extremely resistant to change • HIV infection is likely to continue to grow

44. Uganda • Uganda has a highly clustered, differentiated network that is subject to collapse, but can also grow • Ugandan sexual networks are unstable, currently growing slightly, and will continue to fluctuate

45. In conclusion,

46. Differences … • The differences between South African and Ugandan HIV trends, and the characteristics of each, is largely a property of the network as a whole, and is variably affected by standard interventions such as behaviour change, mortality, ARV roll out, and any other factors at the level of the individual

47. Wealth and poverty? • Wealth and poverty as global statistical measures are less likely to be relevant to HIV prevalence than the social structures by which wealth is distributed and controlled.