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80% of New HIV Transmissions Linked to Gaps in Treatment, Undiagnosed Individuals

A new CDC report suggests that 80% of new HIV cases were transmitted by individuals who were unaware they had HIV or who were not receiving consistent care.

In 2016, approximately 38,700 new HIV cases were detected in the United States. Now, a new report from US Centers for Disease Control and Prevention (CDC) suggests that 80% of new HIV cases reported that year were transmitted by individuals who were unaware they had HIV or who were not receiving consistent care.

The findings, published in this week’s CDC Morbidity and Mortality Weekly Report, were discovered when a team of CDC investigators created a model to estimate HIV transmissions rates at various points along the HIV continuum of care. The model was created to focus national and local prevention efforts to eliminate new HIV cases, with an estimated 1.1 million individuals living with HIV in the United States in 2016.

The investigators updated the Progression and Transmission of HIV (PATH 2.0) model to estimate transmission rates by population risk group and age group. The model also tracked people living with HIV infection and their viral load and CD4 counts as they moved along the continuum of care and added individuals who acquired HIV infection throughout the year.

The model found that transmission rates from persons who were infected with HIV and unaware was 16.1 per 100 person-years, and 8.4 per 100 person-years for individuals non-acutely infected and unaware. Populations who were aware of their HIV status but not in care accounted for a transmission rate of 6.6 per 100 person-years, and those receiving HIV care but not virally suppressed accounted for 6.1 per 100 person-years. The percentages of all transmissions generated by each group were 4.0%, 33.6%, 42.6%, 19.8%, respectively.

Not surprisingly, the investigators found that 0% of transmissions were generated by individuals on a regular antiretroviral therapy regimen and virally suppressed, reinforcing the concept of Undetectable Equals Untransmittable (U=U). The investigators suggest that increasing the number of people living with HIV who have achieved viral suppression will be critical to ending the HIV epidemic in the United States.

The model also addressed the highest number of transmissions by risk group and age. The highest transmission rate was detected among men who have sex with men (MSM), which the investigators attribute to high proportions of MSM who have HIV and the increased risks of transmission associated with anal sex.

When sorted by age group, the highest transmission rate was reported in individuals aged 13—24 years, and the highest number of transmissions came from the population aged ≥55 years, which was attributed to the larger number of people living with HIV in this age group.

“To control the spread of HIV in the United States, HIV infection must be diagnosed early and persons with HIV infection quickly engaged in sustained care and treatment,” the investigators write in the report, further indicating that clinicians should screen patients for HIV infection at least once and test patients who are at a higher risk more frequently.

Moreover, for patients who are identified as having HIV, it is important to engage the patient in consistent antiretroviral therapy and provide education on viral suppression and U=U to decrease the stigma associated with HIV and encourage patients to remain in care.

“Importantly for physicians, if they talk to their patients about U=U ,or not being infectious, it's important that physicians also clearly demonstrate with their nonverbal communication and in words that there's no risk, and [the patient] does not have to be afraid,” Pietro Vernazza, MD, chief of the infectious disease division at Kantonsspital St. Gallen, in Switzerland, and first author of the Swiss Statement, told Contagion® in an interview at CROI 2019. “Once you have very good treatment that results in suppressed viral load, you're fine it's okay, and it will remain so.”

“Together, these approaches can reduce undiagnosed HIV infection in the United States and thereby decrease transmission from persons with undiagnosed infection,” the investigators conclude.