Australian clinic records show significant reduction in duration of infectiousness in HIV-positive gay men from 2007-2016

The period during which HIV-positive men who have sex with men (MSM) are potentially infectious fell significantly between 2007 and 2016, investigators from Australia report in the online edition of AIDS. Data from Melbourne Sexual Health Centre showed that the intervals between HIV infection and diagnosis, between diagnosis to viral suppression and between infection to viral suppression all fell significantly during the study period. The proportion of people with serological evidence of recent infection also more than doubled.

“The estimated duration of infectiousness…fell more than fivefold from 49.0 months for patients diagnosed between 2007 and 2009 and 9.6 months in those diagnosed between 2015 and March 2016,” comment the authors. “If replicated across the community, this reduction in the period of infectiousness could be expected to have a substantial impact on HIV transmission and incidence.”

Viral suppression is associated with reductions in the transmission of HIV at both the community and individual level. People with an undetectable viral load have a very low – probably as low as zero – risk of transmitting HIV to their sexual partners. A priority of HIV prevention is therefore to reduce the duration in which a person is potentially infectious – the interval between infection and diagnosis and diagnosis and viral suppression.

Encouraging people at risk of HIV to test frequently is the main intervention to reduce the interval between infection and diagnosis. The rapid initiation of antiretroviral therapy (ART) reduces the interval between diagnosis and viral suppression. Modern ART regimens are potent, have few side-effects and are easy to take. International treatment guidelines now recommend that all people should be offered ART, regardless of CD4 cell count because of its health benefits and impact on infectiousness.

Melbourne Sexual Health Centre (MSHC) provides HIV and sexual health testing to in excess of 11,000 MSM a year. Researchers at the clinic wanted to determine the combined effect of early diagnosis of HIV and prompt initiation of ART on the time period in which patients were potentially infectious. They therefore designed a retrospective cohort study involving 437 MSM newly diagnosed at their clinic between 2007 and 2016.

Date of infection was estimated using previous testing history, serological evidence of recent infection or baseline CD4 cell count. The period between diagnosis and viral suppression was established by a review of clinic notes.

Patients had a median age of 30 years and a third of individuals were also diagnosed with another sexually transmitted infection on the day of their HIV diagnosis.

Over the nine years of the study, the proportion of patients with serological evidence of recent HIV infection more than doubled, from 15.6% in 2007 to 34.3% in 2016 (p < 0.001). These individuals had significantly higher viral loads and CD4 cell counts than individuals without evidence of very recent infection (p < 0.001).

The median time to diagnosis among patients with a known date of a previous HIV-negative result or serological evidence of recent infection fell significantly from 5.4 months to 4.2 months (p = 0.0054). After inclusion of patients without a previous testing history or serological data, in whom time to diagnosis was based on CD4 cell count, the median interval between infection and diagnosis fell from 6.8 months to 4.3 months (p = 0.0004).

A significant decline was also observed in the median interval between diagnosis and viral suppression, from 22.7 months to 3.2 months (p < 0.001). The overall period of potential infectiousness declined from 49 months for patients diagnosed between 2007 and 2009 to 9.6 months for patients diagnosed in 2015 and 2016 (p < 0.001).

“About one third of HIV diagnoses in MSM in the state of Victoria are made at MSHC. If replicated across the community, the reduction in duration of infectiousness and the increase in the proportion with recent infection can be expected to have had a profound influence on HIV incidence,” write the investigators. “Additionally, a government program now provides PrEP free of charge for 3,600 individuals in the state [of Victoria]. A reduction in both the number of infectious and susceptible individuals can be expected to be complementary or synergistic.”

Changes in testing practices and treatment guidelines appeared to be behind the improvements detected in the study. Diagnosis in a more recent time period was associated with increased chances of having serological evidence of recent infection, a shorter time to viral suppression and a shorter duration of infectiousness.

Men with a history of injecting drug use, as well as individuals who had recently arrived in Australia from a non-English-speaking country, were less likely to be diagnosed promptly and to achieve rapid viral suppression. “This is significant because these groups have been identified as likely to experience delayed care,” comment the authors.

“The duration of infectiousness in MSM diagnosed with HIV at MSHC in Victoria has fallen dramatically between 2007 and 2016 and the proportion diagnosed with serological evidence of recent infection has significantly increased,” conclude the researchers. “This effect is across all population subgroups and marks a very positive milestone for the treatment as prevention paradigm.”