Understanding the Epidemiology and Transmission Dynamics of the HIV/AIDS Pandemic

1. Understanding the Epidemiology and Transmission Dynamics of the HIV/AIDS Pandemic James Chin, MD, MPH Clinical Professor of Epidemiology School of Public Health, University of California, Berkeley E-mail: jchin@socrates.berkeley.edu CCIH, May 2003

2. Two HIV/AIDS Paradigms • In the absence of effective HIV/AIDS prevention and control programs, it is just a matter of time before HIV epidemics will occur in all current low HIV prevalence populations. • “Let's stop the nonsense of trying to determine a 'natural limit' to the [AIDS] epidemic in Asia and the Pacific…” • 2. HIV prevalence can only rise to the levels permitted by the patterns and prevalence of HIV risk behaviors and therefore HIV epidemics will not occur in populations with low levels of HIV risk behaviors. • “It is epidemiologic nonsense to deny that there are no natural limits to epidemic HIV transmission based on the pattern(s) and prevalence of HIV risk behaviors!”

3. Natural History of HIV Infection • Infection is probably lifelong, and severe immune deficiency will develop in up to half of infected adults within 7-8 years. • Annual progression rates from HIV infection to AIDS is similar in Haiti, Thailand, Uganda, and “Western” countries. • Once sufficient immune damage occurs, the infected person becomes susceptible to opportunistic infections and cancers. • These infections and cancers are surrogate indicators of the immunodeficiency due to HIV • Survival after the onset of AIDS is, in the absence of anti-HIV treatment, short and is usually less than 1 year in developing countries.

4. Sexual Transmission of HIV • Results from sex partner studies – per coital act: Padian (USA): Male to female = 1/1,000 • Female to male = 1/8,000 • Gray (Uganda): Male to female = 1/1,000 • Female to male = 1/900 • Facilitating factors (are not co-factors!) include any factor that can cause lesions in the genital or rectal epithelium such as: any concurrent STD, especially ulcerative ones like genital herpes (HSV-2) and chancroid; “dry sex”; lack of male circumcision(?); frequent and traumatic sex, etc., etc. • Anal intercourse is probably more efficient for HIV transmission because of increased tissue trauma.

5. Patterns of Sexual HIV Transmission • The epidemic pattern, where Ro of HIV is > 1, has only occurred where there are: (a) high-risk patterns of sex partner exchange and mixing, i.e., having multiple and concurrent sex partners; and (b) a high prevalence of factors that can facilitate the sexual transmission of HIV. • The non-epidemic pattern, where Ro of HIV is, on average, < 1, occurs from HIV-infected persons (regardless of how they were infected) to their regular sex partner(s). Further HIV spread from these regular partners (i.e., the epidemic pattern) can only occur if these partners have other sex partners. • HIV prevalence will not exceed one percent of the total 15-49 year old population unless the epidemic pattern is prevalent in the heterosexual population.

8. How Reliable are HIV Prevalence Estimates? • Estimation of HIV prevalence is more of an art than a science. With the known vagaries inherent in HIV serologic data and the limitations of the data, methods, and assumptions used, estimation of HIV numbers cannot be precise. • However, current UNAIDS/WHO estimates of most national HIV/AIDS numbers are reasonably accurate. • For high (> 1% of the 15-49 year old population) HIV prevalence countries, estimates can be off by up to 50%; for moderate (> 0.1% < 1%) HIV prevalence countries, estimates can easily be off by 1-2 folds, and for low (> 0.1%) HIV prevalence countries, estimates can be off by several folds!

14. Estimated HIV Prevalence in 10,000 Pregnant Females

15. Risk Behaviors and Disease Alcohol and alcoholism Smoking and lung cancer Sexual risk behaviors and HIV/AIDS

16. Gradient of Sexual HIV Risk Behaviors Highest – (A) “Bathhouse” type settings for MSM where large numbers of MSM had up to 10-20 sex contacts in a single day or night. (B) Large brothel type establishments where FSW have thousands of male clients per year. Moderate – Unprotected vaginal or anal intercourse with multiple partners on a concurrent basis and involving many different sex partners per year. Examples include MSM in moderate size sex networks, “Indirect” FSW in bars, etc., and a large percent (20-40%) of some “general” populations in SSA. Low – Unprotected sexual intercourse with several different partners per year, but mostly on a serial basis.

19. Concluding Comments (1) • The common thread that runs through all epidemic HIV transmission is that the major HIV risk behavior groups affected (MSM, IDU, FSW and their clients) are all socially marginalized and they engage in socially unaccepted and often illegal behavior(s), whereas non-epidemic sexual HIV transmission is generally via legally and morally sanctioned sex. • The risk behaviors for epidemic HIV transmission (unprotected sexual intercourse with multiple and concurrent sex partners) and sharing drug injecting equipment with many other IDU are difficult subjects for official agencies and especially religious groups to deal with.

20. Concluding Comments (2) • All communities, including social and religious institutions, must understand and accept that cultural, social, religious, economic and many other factors influence and/or determine the patterns and prevalence of sex outside of mutually monogamous sex relationships. • Not all “immoral” sex poses a significant risk of sustained or epidemic HIV transmission. A pattern of multiple and concurrent sex partners is required to sustain epidemic HIV transmission. • Substance abuse problems such as IDU should be managed primarily as a public health problem and not as a criminal or “social evils” problem.

21. Take Home Message/Question • Epidemic HIV transmission requires risk behaviors such as having unprotected sexual intercourse with multiple and concurrent sex partners or routinely sharing needles and syringes with other IDU. • The primary question that Christian organizations should ponder is: • Would Christ just fixate on the ABCs of HIV prevention or would he also aggressively support the 100% condom program for all casual and commercial sex, and promote needle exchange programs for IDU?