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Objective:

To obtain insight in the HIV-1 transmission networks among men having sex with men (MSM) in the Netherlands.

Design:

A phylogenetic tree was constructed from polymerase sequences isolated from 2877 HIV-1 subtype B-infected patients monitored as part of the AIDS Therapy Evaluation in the Netherlands (ATHENA) nationwide observational cohort.

Methods:

For MSM with a known date of infection, the most similar sequences were selected as potential transmission pairs when they clustered with bootstrap value of at least 99%. Time from infection to onward transmission was estimated as the median time between dates of infection for each transmission pair. The source of infections with a resistant strain was traced using the entire phylogenetic tree.

Results:

Of sequences from 403 MSM with a known date of infection between 1987 and 2007, 175 (43%) formed 63 clusters. Median time to onward …