Exercises

Exercise 1

Objective

Examine factors affecting the geographic distribution of HIV infection using UNAIDS reports.

Instructions

A compilation of the information available on country-specific HIV/AIDS epidemics is available from the UNAIDS/WHO Working Group on Global HIV/AIDS and STI Surveillance. In collaboration with national AIDS programs, UNAIDS and WHO compile and publish current data on the epidemic in country-specific Epidemiological Fact Sheets. These fact sheets and their updates include recent data on HIV/AIDS prevalence and incidence, and behaviors which affect HIV transmission. Recent fact sheets are available at http://data.unaids.org/publications/Fact-Sheets01.

In this exercise, you will investigate the characteristics of geographic clustering of HIV prevalence in Kenya and India. Your analysis will be based on information from the 2004 Epidemiological Fact Sheet Update for each of these countries. The most recent updates are available on the internet.

For this exercise, you will use estimates of HIV prevalence among pregnant women attending antenatal clinics (ANC). In countries with generalized epidemics (defined by UNAIDS/WHO as countries in which HIV prevalence in pregnant women is above 1 percent on a national level), prevalence among pregnant women is considered to be a good proxy for overall adult prevalence.12

1. Kenya

The information you will need to answer the following questions is found on pages 2 through 5 of the 2004 Epidemiological Fact Sheet for Kenya. (Link to Kenya pdf)

a. There were 22 sites where ANC women were tested in 2001, shown on page 4 of the Fact Sheet. What is the range (e.g., the highest and the lowest) in HIV prevalence among pregnant women reported by these sites?

b. Is there any evidence that HIV prevalence is higher in urban areas? Explain.

c. Use the map on page 5 to describe the geographic distribution of HIV infection in Kenya.

2. India

The information you will need to answer the following questions is found on pages 2 through 5 and in the Annex of the 2004 Epidemiological Fact Sheet for India. (Link to India pdf)

a. What is the range (e.g., the highest and the lowest) in HIV prevalence among pregnant women reported by ANC sites in 2002? (Use the summary of urban and rural ANC surveillance date from 2002, shown on page 4 of the Fact Sheet, to answer this question.)

b. At what proportion of the sites where ANC women were tested in 2002 was HIV prevalence at least 1 percent? To answer this question you will need to use information on pregnant women at the 186 ANC surveillance sites shown in the Fact Sheet Annex on pages 18 to 25.

c. Describe the geographic distribution of HIV cases throughout the country using the map on page 5 of the fact sheet.

d. In order to understand trends in HIV prevalence, it is important to have repeated measurements from a surveillance site over time. Using the Fact Sheet Annex beginning on page 18, determine the number of clinics with data for at least three points in time that have experienced a consistent rise in prevalence (clinics that have had at least one increase and no decrease in prevalence in three consecutive observations). If there is surveillance data from a clinic for more than three years, use the three most recent years for this exercise.

e. What modes of HIV transmission are important in India? Use the assessment of the epidemiological situation on page 2 of the Fact Sheet to answer this question.

Exercise 2

Objective

To become familiar with the proximate determinants framework and use it as a tool for identifying and targeting the determinants of HIV transmission.

Instructions

The proximate determinants framework is a conceptual model used to understand the behaviors and conditions that drive the HIV epidemic. It allows us to draw links between context and programs (on the extreme left hand side of the model) and the three biological determinants of HIV transmission (exposure of susceptible to infected persons, efficiency of transmission, and duration of infectivity) on the right hand side. The proximate determinants are the factors that directly affect exposure, infectiousness and duration of infection. Understanding the proximate determinants of transmission allows us to identify contexts (socio-economic conditions such as poverty, socio-cultural conditions such as women's status, or demographic factors such as population age structure) which promote transmission and to develop intervention strategies that target specific aspects of transmission.

In this exercise, you will identify proximate determinants for each of the three biological determinants of HIV transmission. You will then link each proximate determinant with contextual factors that can cause it and intervention programs that can prevent it.

1. Linking proximate determinants with biological determinants of HIV transmission

The following is a list of behaviors and situations which directly affect the three biological determinants of HIV. Transmission efficiency has been broken down into two subcategories: susceptibility to becoming infected, and infectiousness (ability to infect someone else). Identify the biological determinant influenced by each proximate determinant and mark the appropriate column or columns. If you need help, please refer to the proximate determinants framework chart above. The first determinant has been identified for you.

Linking proximate determinants with biological determinants of HIV transmission

Proximate DeterminantExposure of susceptible to infected personsTransmission Efficiency:Duration of infectivity
SusceptibilityInfectiousness
Condom use   × ×  
Unsafe injections (reuse of needles, for example)      
Concurrency (having sexual partnerships that overlap)      
Coital frequency (how often a person has sex)      
Needle sharing      
Number of new sexual partners      
Circumcision      
Abstinence      
STI (being infected with another sexually transmitted infection)    
Blood bank safety      
How needles and syringes are handled      
Age difference of sexual partners      
Age at first sex      
Older men partnering with younger girls for casual sex      
Injection drug user mixing patterns      

2. Understanding the relationship between underlying, proximate, and biological determinants

In this step, you will examine the biological transmission effects and the underlying determinants: new sexual partner acquisition.

Which biological determinant of HIV transmission is affected by new sexual partner acquisition? What are some underlying contextual determinants (socio-economic, socio-cultural, or demographic) of new partner acquisition? What kinds of intervention strategies could impact new sexual partner acquisition?

3. Visualizing relationships within the proximate determinant framework

Print the empty proximate determinant diagram below. Fill in the diagram with the proximate determinant that you explored in question 2 (new sexual partner acquisition), placing it in the correct box. Add contextual or intervention determinants in the left hand column which could impact this proximate determinant.

PLACE Chart 2

4. PLACE seeks to reduce transmission efficiency among those most likely to be exposed to HIV. How do each of the following reflect this approach and how do each of the following fit into the Proximate Determinants framework?

a. PLACE locates public venues where people meet new sexual partners

b. PLACE finds locations where injection drug users socialize

c. Treating STDs in members of mobile populations

d. Providing condoms at places where sex workers solicit clients

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