In spite of public health prevention campaigns to raise awareness of high-risk behavior for HIV transmission, about 300 new HIV cases are diagnosed every year in Denmark. To determine how to target future prevention programs, researchers investigated the role of late presenters, persons with a CD4 T-cell count of less than 200 cells at diagnosis, in driving the HIV epidemic.
The researchers performed phylogenetic analysis to identify transmission clusters in a study of 1,515 individuals newly diagnosed in Denmark since 2001. About one-fifth of the individuals had primary infections, and 460 were diagnosed late. A total of 696 infections were in gay men. The researchers identified 46 epidemic clusters involving 502 patients. The median cluster size was 7 patients (range 4–82). People in transmission clusters had a significantly higher CD4 cell count and higher viral loads than those who could not be identified in transmission networks. Half of all individuals with a primary HIV infection could be placed in a cluster, compared to only 22 percent of those who were diagnosed late. Other factors such as a young age (under 30 years), intravenous drug use, and men who had sex with men were significantly associated with being in a cluster. Large clusters involved significantly more homosexual transmission, primary infections, younger age, higher CD4 T-cell count, and lower viral load.
Findings show that persons with lower CD4 T-cell counts contributed less to the epidemic than those with higher CD4 T-cell counts. Researchers concluded that the epidemic is driven by mostly younger homosexual men, diagnosed with a primary infection. They recommended that prevention efforts should focus on young gay men, particularly those at risk of primary infection. The study titled, “Phylogenetics of the Danish HIV epidemic: The Role of Very Late Presenters in Sustaining the Epidemic,” was published online ahead of print in the Journal of Acquired Deficiency Syndromes (doi: 10.1097/QAI.0b013e318276becc).