Go Where the Virus Is: An HIV Micro-epidemic Control Approach to Stop HIV Transmission.

Abstract

Globally, a growing majority (59%) of an estimated 38 million people living with HIV (PLHIV) know their HIV status and have achieved HIV viral suppression by adhering to antiretroviral therapy (ART).1 Individuals who achieve sustained viral suppression and undetectable levels of circulating virus through good adherence to ART live long, healthy lives and will not transmit HIV through sexual contact.2–4 The evidence that people who have achieved undetectable viral loads will not transmit HIV sexually—that “undetectable equals untransmittable” (U=U)—underscores the prevention benefits of treatment and the rationale for the global call to achieve near-universal access to ART and viral suppression among PLHIV.4–6 Conversely, HIV viral burden (viremia), generally measured by plasma viral load (HIV RNA copies/mL) assays, is the primary predictor of HIV-related disease progression, morbidity, mortality, and ongoing transmission.4,7 Essentially all HIV transmission originates from a shrinking minority of PLHIV globally (41%) who do not know their HIV infection status or have not yet achieved viral suppression,8 making support for these individuals and their risk contacts a priority for treatment and prevention efforts. Studies have identified a dose-response relationship in which each 10-fold increase in HIV plasma viral load results in an increased relative risk of HIV transmission of 2.5 to 2.9 per sexual contact.9,10 Emerging evidence suggests that even under conditions of near-universal HIV treatment coverage, high viremia and high levels of risk behavior among unserved or underserved PLHIV can sustain epidemic HIV transmission.11,12 In a recent U.S. study of HIV patients in care with a detectable viral load, only a small proportion of PLHIV reported concurrent sexual transmission risk behaviors, but most of the individuals in this group had considerably elevated viral loads, increasing the probability of transmission. The study found that viral loads were likely to be lower among those with a detectable viral load who reported always using condoms.13 High viral burden associated with acute HIV infection (AHI) is a particular concern. Acute infection is characterized by a 2–4-week period of exceptionally high viremia as HIV replicates rapidly in the body before a person’s immune system mounts a response and reduces the level of circulating virus to much lower—but typically not undetectable—levels for a period of months to years.14,15 Although only a small proportion of all PLHIV will be in this brief AHI phase at any given time, per-sex-act transmission probabilities are considerably higher during periods of acute as compared to chronic HIV infection.9,16–18 In key populations engaged in frequent behavioral risks, up to an estimated 50% of all HIV transmission occurs from individuals during AHI when viremia is very high prior to the development of an immune response including anti-HIV antibodies (Ab) that yield reactivity on third-generation Ab assays.14,17,19–24 The provision of ART during AHI and of HIV pre-exposure prophylaxis (PrEP) to the risk-network contacts of acutely infected individuals could prevent a substantial proportion of ongoing HIV transmission. An analysis in Thailand suggested that early diagnosis and treatment during AHI among men who have sex with men could avert 89% of all new infections in this population.25 Approaches that differentiate service delivery to better address the preferences and needs of unserved and underserved individuals have been identified as a priority to close outstanding gaps in access to HIV prevention and treatment.26 In implementing differentiated services, it is increasingly clear that a focus on individuals and networks with the greatest viral burdens has strategic benefit. For example, programs typically transition individuals who are receiving HIV treatment and are identified through routine viral load testing as virally suppressed to options for less frequent clinical follow-up and multimonth dispensing of their antiretroviral medications. This differentiation offers additional convenience to patients and frees up resources and provider time to focus support on virally unsuppressed individuals with greater adherence, clinical, social support, and other needs. Open in a separate window Liz Brenda Kandeyi, nurse (left), takes a client through the steps for clinical services at Kikuyu Sasa Center, Nairobi, Kenya. © 2017 Nancy Coste/FHI 360