Transmission Network Parameters Estimated From HIV Sequences for a Nationwide Epidemic

Methods. A phylodynamic analysis was performed on partial pol gene sequences obtained for routine clinical care from 14 560 individuals, representing approximately 60% of the HIV-positive men who have sex with men (MSM) under care in the United Kingdom. Results. Among individuals linked to others in the data set, 29% are linked to only 1 individual, 41% are linked to 2-10 individuals, and 29% are linked to >= 10 individuals. The right-skewed degree distribution can be approximated by a power law, but the data are best fitted by a Waring distribution for all time depths. For time depths of 5-7 years, the distribution parameter lies within the range that indicates infinite variance. Conclusions. The transmission network among UK MSM is characterized by preferential association such that a randomly distributed intervention would not be expected to stop the epidemic.