Fig. 1

Recruitment networks in Maputo and Nampula/Nacala, BBS-PWID, 2013–2014. Seven seeds were selected in Maputo, of which five participated in the survey and only three seeds recruited participants. The chain of one seed reached 252 participants, the second reached 80 participants, and the third chain reached19 participants. In Maputo the maximum number of recruitment waves was 13. Five seeds were selected in Nampula/Nacala, however, only one seed recruited 123 of the participants in the survey. The maximum number of recruitment waves in Nampula/Nacala was 11. In Maputo, all five seeds that participated in the survey were 35 years old or older and along the processes the participants age become more diversified. In Nampula/Nacala the seed that contributed most in the recruitment of participants was in the 18–24 years old group, and subsequently there was an age diversification