Approximately a third of young people newly linked to HIV care in the United States have viral loads that indicate a high risk of onward transmission, according to research published in the online edition of AIDS. Young men who have sex with men (MSM) had a mean viral load of approximately 125,000 copies/ml, significantly higher than the average of 47,000 copies/ml recorded in their heterosexual peers.
Moreover, a potentially highly infectious viral load of 50,000 copies/ml or above was recorded in 30% of young MSM compared to 22% of young heterosexual people. “These viral load levels are associated with high rates of transmission,” comment the authors. “YMSM [young MSM] are well represented in these data…and they have the highest viral loads, which is consistent with the high rates of ongoing transmission in this population in the United States.”
However, the results may not be entirely bad news. The investigators acknowledge the high viral loads they recorded could be because young people are being diagnosed promptly.
The study involved people aged between 12 and 24 years who were newly linked to HIV care in 2010-11.
Late diagnosis is an important factor underlying much of the HIV-related illness and death that still occurs in the United States. The National HIV/AIDS Strategy therefore emphasises the importance of improving both diagnosis rates and the proportion of people linked and retained in care. Linkage to care also has public health benefits, enabling people to access antiretroviral therapy and thereby reducing their risk of passing HIV on to sexual partners. A 'test and treat' strategy is viewed by some as being a way of controlling the epidemic. Approximately a quarter of new HIV infections in the United States involve people aged between 13 and 24 years, and 87% of all infections in young people involve young MSM. The SMILE in Caring for Youth project is a multi-agency collaboration to improve rates of HIV diagnosis and linkage to care among people aged between 12 and 24. Investigators from the project wished to describe the CD4 cell counts and viral load characteristics of young people newly engaging with HIV care.
They analysed the medical records of 1409 people linked to HIV care at 15 sites across the United States and Puerto Rico in 2010-11. A total of 852 people had both CD4 and viral load results and were eligible for inclusion in the study.
Mean baseline CD4 cell count and viral load were 456 cells/mm3 and 94,398 copies/ml, respectively.
The majority of participants were men (78%) and 68% identified as homosexual/bisexual.
Men had higher mean viral load than women (106,681 copies/ml vs 47,723 copies/ml). There was a significant association between lower CD4 cell count and higher viral load (p < 0.0001).
Sexuality was also associated with viral load, which was significantly higher in MSM than heterosexual people (p = 0.027). Viral load also differed according to mode of HIV acquisition, and was significantly higher among men who acquired HIV through sex with other men, compared to individuals who acquired the infection through heterosexual contact or as a result of vertical (mother to child) transmission (p < 0.0001).
A little under a third (31%) of homosexual/bisexual men had a viral load above 50,000 copies/ml compared to 22% of heterosexual people. Similarly, 31% of men who acquired HIV through sex with another man had a viral load of 50,000 copies/ml or greater compared to 20% of people who acquired HIV at birth and 18% of individuals who acquired HIV through heterosexual contact.
“Our findings suggest that the population of HIV-infected youth may be a highly infectious population,” write the authors. They believe that the high viral load observed in their study participants could be because of prompt diagnosis. “As supported by our higher CD4 cell counts and proportions with CD4 cell count more than 350 (over 2/3) compared with adults (43%), youth are more likely diagnosed closer to their time of infection than adults and therefore, viral dynamics may skew viral load data.”
The authors recommend “any public health test and treat strategy put a strong emphasis on youth, particularly YMSM.”
Ellen JM et al. HIV viral load levels and CD4+ cell counts of youth in 14 US cities. AIDS 28, online edition. DOI: 10.1097/QAD.0000000000000183, 2013.