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"Medical Journeys" is a set of clinical resources reviewed by physicians, meant for the medical team as well as the patients they serve. Each episode of this journey through a disease state contains both a physician guide and a downloadable/printable patient resource. "Medical Journeys" chart a path each step of the way for physicians and patients and provide continual resources and support, as the caregiver team navigates the course of a disease.

Viral load is the key to measuring success of HIV treatment, as a reduced viral load after the initiation of antiretroviral therapy (ART) is associated with a lower chance of disease progression and death.

Measured , viral load can range from as many as 1,000,000 copies/mL or more to "undetectable," defined as less than 20 copies/mL. The International Association of Providers of AIDS Care (IAPAC) defines as over 100,000 copies/mL, and a "lower" viral load as under 10,000 copies/mL.

"Viral load is the most important indicator of initial and sustained response to ART," wrote the authors of the latest NIH Department of Health and Human Services , published in September 2022, who also called viral load "an established surrogate for treatment response."

The guidelines noted that initial testing of a patient's viral load, prior to initiation of ART, is necessary to determine the appropriate treatment regimen, as "several currently approved [antiretroviral] drugs or regimens have been associated with poorer responses in patients with high baseline viral load." HIV treatment is , at any viral load, and with any CD4 T-cell count.

The guidelines recommended that after initial testing, a patient's viral load should be tested 4-8 weeks following initiation of ART and 4-8 weeks after that, until the viral load falls below the limit of detection.

Once a patient has achieved viral suppression, viral load may then be tested every 3-4 months, or as "clinically indicated." If a patient has been virally suppressed for more than a year on a stable ART regimen, the interval between tests may be extended to every 6 months, the guidelines state.

Game-Changing Studies on Viral Suppression

CDC as less than 200 copies/mL, and an "undetectable" viral load as less than 20 copies/mL (below the limit of detection of available assays for HIV-1). IAPAC noted that if a patient is adherent to treatment, they may achieve viral suppression within 8-24 weeks after initiation of ART.

Importantly, if a patient has an undetectable viral load, they are unable to sexually transmit HIV to their partners. This game-changing conclusion was the result of several studies among heterosexual patients and men who have sex with men (MSM).

The catalyst was the ground-breaking study, published in the New England Journal of Medicine in 2016. While this study set out to examine HIV transmission in serodiscordant heterosexual couples randomized to early ART compared with those assigned to delayed ART, the authors found eight genetically linked infections in the early-ART group whose partners were most likely viremic at the time of infection.

"The relationship between viremia and HIV transmission ... emphasizes the importance of counseling with respect to the potential for HIV-1 transmission before viral suppression is achieved, of close monitoring of the viral load during treatment, and of responding quickly in cases of ART failure," the researchers wrote.

The observational , published in The Lancet in 2019, found that with a median 2.0 "couple-years of follow-up," there were zero instances of genetically linked HIV transmission between serodiscordant MSM couples engaging in condomless anal sex when the partner with HIV was virally suppressed.

"Despite all the concerns about potential risks, there has not been a single verified case of HIV transmission in the context of complete virally suppressive ART reported in the literature," the authors wrote. The study results also "support wider dissemination of the message of the U=U [undetectable equals untransmittable] campaign that risk of transmission of HIV in the context of virally suppressive ART is zero."

And while the evidence was not nearly as robust, the guidelines noted that undetectable viral load may also be associated with a lower risk of other forms of HIV transmission. Undetectable viral load substantially reduced the risk of congenital transmission among people who are able to become pregnant and transmission through breast milk to infants.

Undetectable viral load may also reduce the risk of transmitting HIV through injection drug use, the document states.

Vital Rebound

The guidelines caution that even though patients may have an undetectable viral load, they may still experience , or , where it may jump up to a detectable level that is generally low despite adherence to ART. These fluctuations, however, are "usually not predictive of virologic failure," as long as the next viral load measurement is undetectable.

Otherwise, lack of adherence to treatment is likely the main reason for an increase in a patient's HIV viral load. Other reasons may include drug resistance or a mutation.

The document added that the AIDS Clinical Trials Group now defines virologic failure as "the inability to achieve or maintain" a viral load of less than 200 copies/mL, thus eliminating "most cases of apparent viremia caused by viral load blips or assay variability."

Educating Patients About U=U

Initially published by the Prevention Access Campaign (PAC), the concept of U=U morphed into a public health campaign to provide education and prevent stigma toward those living with HIV.

Moreover, U=U does not distinguish between "virally suppressed" and "undetectable viral load." According to the PAC website, "for the purposes of the U=U campaign, the terms 'undetectable' and 'virally suppressed' mean the same thing."

The HIV Medicine Association (HIVMA) emphasized the , adding that it can be "transformative" for their "interpersonal relationships," and that because patients cannot transmit HIV with an undetectable viral load, "they can still be touched and loved."

HIVMA stressed the importance of counseling patients about staying on ART and taking their medicine every day, as well as encouraging them to keep their medical appointments so they can ensure they stay undetectable.

Summary

Checking the viral load and CD4 T-cell count as part of the , then monitoring the HIV-1 viral load as a response to treatment, is the cornerstone of HIV treatment. Suppression of HIV means that HIV cannot be transmitted sexually, and the U=U campaign has made progress in reducing stigma for people with HIV.

Read previous installments in this series:

Part 1: The Evolution of HIV: From Death Sentence to Chronic Condition

Part 2: Antiretroviral Therapy for HIV: When Less May Be More

Up next: PrEP: Pills, Shots and Stigma