Outcome of HIV Testing Among Family Members of Index Cases Across 36 Facilities in Abidjan, Côte d'Ivoire.

In Côte d'Ivoire, the Family Approach to Counseling and Testing (FACT) program began in 2015 and provides facility-based HIV testing to the sexual partners, children and other household family members of HIV-positive index cases. We evaluated whether the FACT program is an effective approach to HIV case finding. We reviewed 1762 index patient charts to evaluate outcomes of the FACT program, held across 36 facilities in Abidjan. Index cases enumerated a total of 644 partners, 2301 children and 508 other family members including parents and siblings. Among the partners tested for HIV, the positivity rate was 21%; for children the positivity rate was 5% and for all other family members the positivity rate was 11%. Offering HIV testing services to the family members of HIV positive index cases is an effective approach to case finding in Côte d'Ivoire. Particularly, offering HIV testing to the partners of positive women index cases can be key to identifying previously undiagnosed men and linking them to treatment.

Partner Notification Approaches for Sex Partners and Children of Human Immunodeficiency Virus Index Cases in Côte d'Ivoire.

BACKGROUND: Four partner notification approaches were introduced in health facilities in Côte d'Ivoire to increase human immunodeficiency virus (HIV) testing uptake among the type of contacts (sex partners and biological children younger than 15 years). The study assessed the 4 approaches: client referral (index cases refer the contacts for HIV testing), provider referral (health care providers refer the contacts), contract referral (index case-provider hybrid approach), and dual referral (both the index and their partner are tested simultaneously). METHODS: Program data were collected at 4 facilities from October 2018 to March 2019 from index case files and HIV testing register. We compared uptake of the approaches, uptake of HIV testing, and HIV positivity percentages, stratified by contact type and gender. RESULTS: There were 1089 sex partners and 469 children from 1089 newly diagnosed index cases. About 90% of children were contacted through client referral: 85.2% of those were tested and 1.4% was positive. Ninety percent of the children came from female index cases. The provider referral brought in 56.3% of sex partners, of whom 97.2% were HIV-tested. The client referral brought in 30% of sex partners, of whom only 81.5% were HIV-tested. The HIV positivity percentages were 75.5% and 72.7%, respectively, for the 2 approaches. Male index cases helped to reach twice as many HIV-positive sexual contacts outside the household (115) than female index cases (53). The contract and dual referrals were not preferred by index cases. CONCLUSIONS: Provider referral is a successful and acceptable strategy for bringing in sex partners for testing. Client referral is preferred for children.

Timing of Community Mitigation and Changes in Reported COVID-19 and Community Mobility - Four U.S. Metropolitan Areas, February 26-April 1, 2020.

Community mitigation activities (also referred to as nonpharmaceutical interventions) are actions that persons and communities can take to slow the spread of infectious diseases. Mitigation strategies include personal protective measures (e.g., handwashing, cough etiquette, and face coverings) that persons can use at home or while in community settings; social distancing (e.g., maintaining physical distance between persons in community settings and staying at home); and environmental surface cleaning at home and in community settings, such as schools or workplaces. Actions such as social distancing are especially critical when medical countermeasures such as vaccines or therapeutics are not available. Although voluntary adoption of social distancing by the public and community organizations is possible, public policy can enhance implementation. The CDC Community Mitigation Framework (1) recommends a phased approach to implementation at the community level, as evidence of community spread of disease increases or begins to decrease and according to severity. This report presents initial data from the metropolitan areas of San Francisco, California; Seattle, Washington; New Orleans, Louisiana; and New York City, New York* to describe the relationship between timing of public policy measures, community mobility (a proxy measure for social distancing), and temporal trends in reported coronavirus disease 2019 (COVID-19) cases. Community mobility in all four locations declined from February 26, 2020 to April 1, 2020, decreasing with each policy issued and as case counts increased. This report suggests that public policy measures are an important tool to support social distancing and provides some very early indications that these measures might help slow the spread of COVID-19.

Sex Differences in HIV Testing - 20 PEPFAR-Supported Sub-Saharan African Countries, 2019.

Despite progress toward controlling the human immunodeficiency virus (HIV) epidemic, testing gaps remain, particularly among men and young persons in sub-Saharan Africa (1). This observational study used routinely collected programmatic data from 20 African countries reported to the U.S. President's Emergency Plan for AIDS Relief (PEPFAR) from October 2018 to September 2019 to assess HIV testing coverage and case finding among adults (defined as persons aged ≥15 years). Indicators included number of HIV tests conducted, number of HIV-positive test results, and percentage positivity rate. Overall, the majority of countries reported higher HIV case finding among women than among men. However, a slightly higher percentage positivity was recorded among men (4.7%) than among women (4.1%). Provider-initiated counseling and testing (PITC) in health facilities identified approximately two thirds of all new cases, but index testing had the highest percentage positivity in all countries among both sexes. Yields from voluntary counseling and testing (VCT) and mobile testing varied by sex and by country. These findings highlight the need to identify and implement the most efficient strategies for HIV case finding in these countries to close coverage gaps. Strategies might need to be tailored for men who remain underrepresented in the majority of HIV testing programs.

Scaling Up Testing for Human Immunodeficiency Virus Infection Among Contacts of Index Patients - 20 Countries, 2016-2018.

In 2017, the Joint United Nations Programme on HIV/AIDS (UNAIDS) estimated that worldwide, 36.9 million persons were living with human immunodeficiency virus (HIV) infection, the virus infection that causes acquired immunodeficiency syndrome (AIDS). Among persons with HIV infection, approximately 75% were aware of their HIV status, leaving 9.4 million persons with undiagnosed infection (1). Index testing, also known as partner notification or contact tracing, is an effective case-finding strategy that targets the exposed contacts of HIV-positive persons for HIV testing services. This report summarizes data from HIV tests using index testing in 20 countries supported by CDC through the U.S. President's Emergency Plan for AIDS Relief (PEPFAR) during October 1, 2016-March 31, 2018. During this 18-month period, 1,700,998 HIV tests with 99,201 (5.8%) positive results were reported using index testing. The positivity rate for index testing was 9.8% among persons aged ≥15 years and 1.5% among persons aged <15 years. During the reporting period, HIV positivity increased 64% among persons aged ≥15 years (from 7.6% to 12.5%) and 67% among persons aged <15 years (from 1.2% to 2.0%). Expanding index testing services could help increase the number of persons with HIV infection who know their status, are initiated onto antiretroviral treatment, and consequently reduce the number of persons who can transmit the virus.

Cost of Community-Based HIV Testing Activities to Reach Saturation in Botswana.

In Botswana, 85% of persons living with HIV are aware of their status. We performed an economic analysis of HIV testing activities implemented during intensive campaigns, in 11 communities, between April 2015 and March 2016, through the Botswana Combination Prevention Project. The total cost was $1,098,312, or $99,847 per community, with 60% attributable to home-based testing and 40% attributable to mobile testing. The cost per person tested was $44, and $671 per person testing positive (2017 USD). Labor costs comprised 64% of total costs. In areas of high HIV prevalence and treatment coverage, the cost of untargeted home-based testing may be inflated by the efforts required to assess the testing eligibility of clients who are HIV-positive and on ART. Home-based and mobile testing delivered though an intensive community-based campaign allowed the identification of HIV positive persons, who may not access health facilities, at a cost comparable to other studies.

From Theory to Practice: Implementation of a Resource Allocation Model in Health Departments.

OBJECTIVE: To develop a resource allocation model to optimize health departments' Centers for Disease Control and Prevention (CDC)-funded HIV prevention budgets to prevent the most new cases of HIV infection and to evaluate the model's implementation in 4 health departments. DESIGN, SETTINGS, AND PARTICIPANTS: We developed a linear programming model combined with a Bernoulli process model that allocated a fixed budget among HIV prevention interventions and risk subpopulations to maximize the number of new infections prevented. The model, which required epidemiologic, behavioral, budgetary, and programmatic data, was implemented in health departments in Philadelphia, Chicago, Alabama, and Nebraska. MAIN OUTCOME MEASURES: The optimal allocation of funds, the site-specific cost per case of HIV infection prevented rankings by intervention, and the expected number of HIV cases prevented. RESULTS: The model suggested allocating funds to HIV testing and continuum-of-care interventions in all 4 health departments. The most cost-effective intervention for all sites was HIV testing in nonclinical settings for men who have sex with men, and the least cost-effective interventions were behavioral interventions for HIV-negative persons. The pilot sites required 3 to 4 months of technical assistance to develop data inputs and generate and interpret the results. Although the sites found the model easy to use in providing quantitative evidence for allocating HIV prevention resources, they criticized the exclusion of structural interventions and the use of the model to allocate only CDC funds. CONCLUSIONS: Resource allocation models have the potential to improve the allocation of limited HIV prevention resources and can be used as a decision-making guide for state and local health departments. Using such models may require substantial staff time and technical assistance. These model results emphasize the allocation of CDC funds toward testing and continuum-of-care interventions and populations at highest risk of HIV transmission.

An Evaluation of an Enhanced Model of Integrating Family Planning Into HIV Treatment Services in Zambia, April 2018-June 2019.

BACKGROUND: We designed and implemented an enhanced model of integrating family planning (FP) into existing HIV treatment services at 6 health facilities in Lusaka, Zambia. METHODS: The enhanced model included improving FP documentation within HIV monitoring systems, training HIV providers in FP services, offering contraceptives within the HIV clinic, and facilitated referral to community-based distributors. Independent samples of women living with HIV (WLHIV) aged ≥16 years were interviewed before and after intervention and their clinical data abstracted from medical charts. Logistic regression models were used to assess differences in key outcomes between the 2 periods. RESULTS: A total of 629 WLHIV were interviewed preintervention and 684 postintervention. Current FP use increased from 35% to 49% comparing the pre- and postintervention periods ( P = 0.0025). Increased use was seen for injectables (15% vs. 25%, P < 0.0001) and implants (5% vs. 8%, P > 0.05) but not for pills (10% vs. 8%, P < 0.05) or intrauterine devices (1% vs. 1%, P > 0.05). Dual method use (contraceptive + barrier method) increased from 8% to 18% ( P = 0.0003), whereas unmet need for FP decreased from 59% to 46% ( P = 0.0003). Receipt of safer conception counseling increased from 27% to 39% ( P < 0.0001). The estimated total intervention cost was $83,293 (2018 USD). CONCLUSIONS: Our model of FP/HIV integration significantly increased the number of WLHIV reporting current FP and dual method use, a met need for FP, and safer conception counseling. These results support continued efforts to integrate FP and HIV services to improve women's access to sexual and reproductive health services.

Health Impact and Cost-Effectiveness of HIV Testing, Linkage, and Early Antiretroviral Treatment in the Botswana Combination Prevention Project.

BACKGROUND: The Botswana Combination Prevention Project tested the impact of combination prevention (CP) on HIV incidence in a community-randomized trial. Each trial arm had ∼55,000 people, 26% HIV prevalence, and 72% baseline ART coverage. Results showed intensive testing and linkage campaigns, expanded antiretroviral treatment (ART), and voluntary male medical circumcision referrals increased coverage and decreased incidence over ∼29 months of follow-up. We projected lifetime clinical impact and cost-effectiveness of CP in this population. SETTING: Rural and periurban communities in Botswana. METHODS: We used the Cost-Effectiveness of Preventing AIDS Complications model to estimate lifetime health impact and cost of (1) earlier ART initiation and (2) averting an HIV infection, which we applied to incremental ART initiations and averted infections calculated from trial data. We determined the incremental cost-effectiveness ratio [US$/quality-adjusted life-years (QALY)] for CP vs. standard of care. RESULTS: In CP, 1418 additional people with HIV initiated ART and an additional 304 infections were averted. For each additional person started on ART, life expectancy increased 0.90 QALYs and care costs increased by $869. For each infection averted, life expectancy increased 2.43 QALYs with $9200 in care costs saved. With CP, an additional $1.7 million were spent on prevention and $1.2 million on earlier treatment. These costs were mostly offset by decreased care costs from averted infections, resulting in an incremental cost-effectiveness ratio of $79 per QALY. CONCLUSIONS: Enhanced HIV testing, linkage, and early ART initiation improve life expectancy, reduce transmission, and can be cost-effective or cost-saving in settings like Botswana.

Finding, treating and retaining persons with HIV in a high HIV prevalence and high treatment coverage country: Results from the Botswana Combination Prevention Project.

INTRODUCTION: The scale-up of Universal Test and Treat has resulted in reductions in HIV morbidity, mortality and incidence. However, healthcare system and personal challenges have impacted the levels of treatment coverage achieved. We implemented interventions to improve linkage to care, retention, viral load (VL) coverage and service delivery, and describe the HIV care cascade over the course of the Botswana Combination Prevention Project (BCPP) study. METHODS: BCPP was designed to evaluate the impact of prevention interventions on HIV incidence in 30 communities in Botswana. We followed a longitudinal cohort of newly identified and known HIV-positive persons not on antiretroviral therapy (ART) identified through community-based testing activities through BCPP and referred with appointments to local HIV clinics in 15 intervention communities. Those who did not keep the first or follow-up appointments were tracked and traced through phone and home contacts. Improvements to service delivery models in the intervention clinics were also implemented. RESULTS: A total of 3,657 newly identified or HIV-positive persons not on ART were identified and referred to their local HIV clinic; 90% (3,282/3,657) linked to care and of those, 93% (3,066/3,282) initiated treatment. Near the end of the study, 221 persons remained >90 days late for appointments or missing. Tracing efforts identified 54/3,066 (2%) persons who initiated treatment but died, and 106/3,066 (3%) persons were located and returned to treatment. At study end, 61/3,066 (2%) persons remained missing and were never reached. Overall, 2,951 (98%) persons living with HIV (PLHIV) who initiated treatment were still alive, retained in care and still receiving ART out of the 3,001 persons alive at the end of the study. Of those on ART, 2,854 (97%) had current VL results and 2,784 (98%) of those were virally suppressed at study end. CONCLUSIONS: This study achieved high rates of linkage, treatment initiation, retention and VL coverage and suppression in a cohort of newly identified and known PLHIV not on ART. Tracking and tracing interventions effectively identified those persons who needed more resource intensive follow-up. The interventions implemented to improve service delivery and data quality may have also contributed to high linkage and retention rates. Clinical trial number: NCT01965470.

Recommendations for increasing the use of HIV/AIDS resource allocation models.

BACKGROUND: Resource allocation models have not had a substantial impact on HIV/AIDS resource allocation decisions in spite of the important, additional insights they may provide. In this paper, we highlight six difficulties often encountered in attempts to implement such models in policy settings; these are: model complexity, data requirements, multiple stakeholders, funding issues, and political and ethical considerations. We then make recommendations as to how each of these difficulties may be overcome. RESULTS: To ensure that models can inform the actual decision, modellers should understand the environment in which decision-makers operate, including full knowledge of the stakeholders' key issues and requirements. HIV/AIDS resource allocation model formulations should be contextualized and sensitive to societal concerns and decision-makers' realities. Modellers should provide the required education and training materials in order for decision-makers to be reasonably well versed in understanding the capabilities, power and limitations of the model. CONCLUSION: This paper addresses the issue of knowledge translation from the established resource allocation modelling expertise in the academic realm to that of policymaking.

Cost implications of HIV retesting for verification in Africa.

INTRODUCTION: HIV misdiagnosis leads to severe individual and public health consequences. Retesting for verification of all HIV-positive cases prior to antiretroviral therapy initiation can reduce HIV misdiagnosis, yet this practice has not been not widely implemented. METHODS: We evaluated and compared the cost of retesting for verification of HIV seropositivity (retesting) to the cost of antiretroviral treatment (ART) for misdiagnosed cases in the absence of retesting (no retesting), from the perspective of the health care system. We estimated the number of misdiagnosed cases based on a review of misdiagnosis rates, and the number of positives persons needing ART initiation by 2020. We presented the total and per person costs of retesting as compared to no retesting, over a ten-year horizon, across 50 countries in Africa grouped by income level. We conducted univariate sensitivity analysis on all model input parameters, and threshold analysis to evaluate the parameter values where the total costs of retesting and the costs no retesting are equivalent. Cost data were adjusted to 2017 United States Dollars. RESULTS AND DISCUSSION: The estimated number of misdiagnoses, in the absence of retesting was 156,117, 52,720 and 29,884 for lower-income countries (LICs), lower-middle income countries (LMICs), and upper middle-income countries (UMICs), respectively, totaling 240,463 for Africa. Under the retesting scenario, costs per person initially diagnosed were: $40, $21, and $42, for LICs, LMICs, and UMICs, respectively. When retesting for verification is implemented, the savings in unnecessary ART were $125, $43, and $75 per person initially diagnosed, for LICs, LMICs, and UMICs, respectively. Over the ten-year horizon, the total costs under the retesting scenario, over all country income levels, was $475 million, and was $1.192 billion under the no retesting scenario, representing total estimated savings of $717 million in HIV treatment costs averted. CONCLUSIONS: Results show that to reduce HIV misdiagnosis, countries in Africa should implement the WHO's recommendation of retesting for verification prior to ART initiation, as part of a comprehensive quality assurance program for HIV testing services.

S4HARA: System for HIV/AIDS resource allocation.

BACKGROUND: HIV/AIDS resource allocation decisions are influenced by political, social, ethical and other factors that are difficult to quantify. Consequently, quantitative models of HIV/AIDS resource allocation have had limited impact on actual spending decisions. We propose a decision-support System for HIV/AIDS Resource Allocation (S4HARA) that takes into consideration both principles of efficient resource allocation and the role of non-quantifiable influences on the decision-making process for resource allocation. METHODS: S4HARA is a four-step spreadsheet-based model. The first step serves to identify the factors currently influencing HIV/AIDS allocation decisions. The second step consists of prioritizing HIV/AIDS interventions. The third step involves allocating the budget to the HIV/AIDS interventions using a rational approach. Decision-makers can select from several rational models of resource allocation depending on availability of data and level of complexity. The last step combines the results of the first and third steps to highlight the influencing factors that act as barriers or facilitators to the results suggested by the rational resource allocation approach. Actionable recommendations are then made to improve the allocation. We illustrate S4HARA in the context of a primary healthcare clinic in South Africa. RESULTS: The clinic offers six types of HIV/AIDS interventions and spends US$750,000 annually on these programs. Current allocation decisions are influenced by donors, NGOs and the government as well as by ethical and religious factors. Without additional funding, an optimal allocation of the total budget suggests that the portion allotted to condom distribution be increased from 1% to 15% and the portion allotted to prevention and treatment of opportunistic infections be increased from 43% to 71%, while allocation to other interventions should decrease. CONCLUSION: Condom uptake at the clinic should be increased by changing the condom distribution policy from a pull system to a push system. NGOs and donors promoting antiretroviral programs at the clinic should be sensitized to the results of the model and urged to invest in wellness programs aimed at the prevention and treatment of opportunistic infections. S4HARA differentiates itself from other decision support tools by providing rational HIV/AIDS resource allocation capabilities as well as consideration of the realities facing authorities in their decision-making process.

A systematic review on cost effectiveness of HIV prevention interventions in the United States.

BACKGROUND: The Centers for Disease Control and Prevention (CDC) focus on funding HIV prevention interventions likely to have high impact on the HIV epidemic. In its most recent funding announcement to state and local health department grantees, CDC required that health departments allocate the majority of funds to four HIV prevention interventions: HIV testing, prevention with HIV-positives and their partners, condom distribution and policy initiatives. OBJECTIVE: We conducted a systematic review of the published literature to determine the extent of the cost-effectiveness evidence for each of those interventions. METHODOLOGY: We searched for US-based studies published through October 2012. The studies that qualified for inclusion contained original analyses that reported costs per quality-adjusted life-year saved, life-year saved, HIV infection averted, or new HIV diagnosis. For each study, paired reviewers performed a detailed review and data extraction. We reported the number of studies related to each intervention and summarized key cost-effectiveness findings according to intervention type. Costs were converted to 2011 US dollars. RESULTS: Of the 50 articles that met the inclusion criteria, 33 related to HIV testing, 15 assessed prevention with HIV-positives and partners, three reported on condom distribution, and one reported on policy initiatives. Methodologies and cost-effectiveness metrics varied across studies and interventions, making them difficult to compare. CONCLUSION: Our review provides an updated summary of the published evidence of cost effectiveness of four key HIV prevention interventions recommended by CDC. With the exception of testing-related interventions, including partner services, where economic evaluations suggest that testing often can be cost effective, more cost-effectiveness research is needed to help guide the most efficient use of HIV prevention funds.

Estimating per-act HIV transmission risk: a systematic review.

BACKGROUND: Effective HIV prevention programs rely on accurate estimates of the per-act risk of HIV acquisition from sexual and parenteral exposures. We updated the previous risk estimates of HIV acquisition from parenteral, vertical, and sexual exposures, and assessed the modifying effects of factors including condom use, male circumcision, and antiretroviral therapy. METHODS: We conducted literature searches to identify new studies reporting data regarding per-act HIV transmission risk and modifying factors. Of the 7339 abstracts potentially related to per-act HIV transmission risk, three meta-analyses provided pooled per-act transmission risk probabilities and two studies provided data on modifying factors. Of the 8119 abstracts related to modifying factors, 15 relevant articles, including three meta-analyses, were included. We used fixed-effects inverse-variance models on the logarithmic scale to obtain updated estimates of certain transmission risks using data from primary studies, and employed Poisson regression to calculate relative risks with exact 95% confidence intervals for certain modifying factors. RESULTS: Risk of HIV transmission was greatest for blood transfusion, followed by vertical exposure, sexual exposures, and other parenteral exposures. Sexual exposure risks ranged from low for oral sex to 138 infections per 10,000 exposures for receptive anal intercourse. Estimated risks of HIV acquisition from sexual exposure were attenuated by 99.2% with the dual use of condoms and antiretroviral treatment of the HIV-infected partner. CONCLUSION: The risk of HIV acquisition varied widely, and the estimates for receptive anal intercourse increased compared with previous estimates. The risk associated with sexual intercourse was reduced most substantially by the combined use of condoms and antiretroviral treatment of HIV-infected partners.

HIV sexual transmission risk among serodiscordant couples: assessing the effects of combining prevention strategies.

BACKGROUND: The number of strategies to prevent HIV transmission has increased following trials evaluating antiretroviral therapy (ART), preexposure prophylaxis (PrEP) and male circumcision. Serodiscordant couples need guidance on the effects of these strategies alone, and in combination with each other, on HIV transmission. METHODS: We estimated the sexual risk of HIV transmission over 1-year and 10-year periods among male-male and male-female serodiscordant couples. We assumed the following reductions in transmission: 80% from consistent condom use; 54% from circumcision in the negative male partner of a heterosexual couple; 73% from circumcision in the negative partner of a male-male couple; 71% from PrEP in heterosexual couples; 44% from PrEP in male-male couples; and 96% from ART use by the HIV-infected partner. FINDINGS: For couples using any single prevention strategy, a substantial cumulative risk of HIV transmission remained. For a male-female couple using only condoms, estimated risk over 10 years was 11%; for a male-male couple using only condoms, estimated risk was 76%. ART use by the HIV-infected partner was the most effective single strategy in reducing risk; among male-male couples, adding consistent condom use was necessary to keep the 10-year risk below 10%. CONCLUSION: Focusing on 1-year and longer term transmission probabilities gives couples a better understanding of risk than those illustrated by data for a single sexual act. Long-term transmission probabilities to the negative partner in serodiscordant couples can be high, though these can be substantially reduced with the strategic use of preventive methods, especially those that include ART.

Estimating the impact of state budget cuts and redirection of prevention resources on the HIV epidemic in 59 California local health departments.

BACKGROUND: In the wake of a national economic downturn, the state of California, in 2009-2010, implemented budget cuts that eliminated state funding of HIV prevention and testing. To mitigate the effect of these cuts remaining federal funds were redirected. This analysis estimates the impact of these budget cuts and reallocation of resources on HIV transmission and associated HIV treatment costs. METHODS AND FINDINGS: We estimated the effect of the budget cuts and reallocation for California county health departments (excluding Los Angeles and San Francisco) on the number of individuals living with or at-risk for HIV who received HIV prevention services. We used a Bernoulli model to estimate the number of new infections that would occur each year as a result of the changes, and assigned lifetime treatment costs to those new infections. We explored the effect of redirecting federal funds to more cost-effective programs, as well as the potential effect of allocating funds proportionately by transmission category. We estimated that cutting HIV prevention resulted in 55 new infections that were associated with $20 million in lifetime treatment costs. The redirection of federal funds to more cost-effective programs averted 15 HIV infections. If HIV prevention funding were allocated proportionately to transmission categories, we estimated that HIV infections could be reduced below the number that occurred annually before the state budget cuts. CONCLUSIONS: Reducing funding for HIV prevention may result in short-term savings at the expense of additional HIV infections and increased HIV treatment costs. Existing HIV prevention funds would likely have a greater impact on the epidemic if they were allocated to the more cost-effective programs and the populations most likely to acquire and transmit the infection.