1) The study defined three categories of injecting drug users (IDUs) in a neighborhood in New York - a core network of 40 IDUs, an inner periphery of 95 IDUs who obtained drugs and assistance from the core, and an outer periphery who purchased drugs independently without interacting with the core. 2) Data was collected through ethnographic observation of hundreds of drug users, 210 interviews, and structured interviews with 767 IDUs where they named their injection partners. 3) Different levels of HIV risk behaviors and infection rates were found among the three network groups, with the core having the highest rates.

1. Tutorial 5
Health networks

2. Curtis, R., Friedman, A., Neaigus, B., Jose, B., Goldstein, M. and Ildefonso, G. (1995)
‘Street-level drug markets: network structure and HIV risk’, Social Networks 17:
229–49.
Observations and survey. Interviews with a selected sample of the participant
who agreed to talk.
Define and situate three categories of injecting drug users (IDUs) - a core, an
inner periphery and an outer periphery - in a street-level drug market scene
in Bushwick, a NY area (originally settled by the Dutch…).
Data from ethnographic fieldwork were used to define a 'core' network of
IDUs, and a formal survey was used to collect data about social ties among
local IDUs. 'Inner‘ and 'outer' peripheral groups are defined in terms of the
presence or absence of direct links to the core.
Different locations in these network structures were associated with different
levels of AIDS risk behaviours and of HIV infection rates.
QL

QN

3. Method
Ethnographic fieldwork, hundreds of drug users (including many non-injectors)
were contacted and observed by the ethnographic staff. The fieldwork generated
several hundred pages of observational notes as well as 210 open-ended interviews
with 68 drug users in the neighborhood.
Structured independent interviews with 767 IDUs were completed in the
project's storefront, and HIV-antibody tests were done on 90% of them.
Questions in the structured interviews which asked respondents to name and
describe their injection partners during the 30 days prior to the interview.
A link between two people is established:
• When a network member arrived at the research storefront accompanied by the
index subject, the pair was considered to be linked
• Through a field link in which the subject pointed out a nominated contact to a
research staff member;
• Through ethnographic observation (i.e. two subjects being seen together in a social
or drug-related interaction by the project's ethnographic staff);
• Through matching a number of key descriptive variables of nominated injecting
network members in the study's field data base (e.g. age within 5 years, first name
or nickname, height within 3 inches, ethnic group, etc.)

4. Large and heterogeneous 'core network' of street-level drug users in the
neighborhood.
The core network was defined by using two types of ethnographically generated
data: observations and self-reports from drug users and distributors. The most
important criterion for inclusion in the core network was validation by other core
network members.
Criteria of inclusion:
• sharing drugs
• drug distributors also contributed to the definition of core network members,
by giving out free sample of a new brand to core members who were likely to
share with others
• Periphery members seek the assistance of core network members to help
them buy drugs (especially heroin) as well as to gain access to local places
where they could use drugs.
40 members of the core network from an eligible sample of 767 IDUs.

6. Any IDU in the formal survey who was not a member of our identified 'core network' was
considered a member of the periphery. The periphery included, among others
(a) people who lived in the neighborhood but were only occasional users of street-level drugs
(b) local residents who used street-level drugs every day but kept strictly to themselves and
used them in the privacy of their homes
(c) daily users who came from other neighborhoods to buy for themselves and their friends
but who did not spend much time in Bushwick.
Members of the inner periphery were primarily defined as
• Those non-core IDUs who said that they had shared drugs locally with at least one member
of the core network within 30 days prior to being interviewed.
• Those named by core network members as injection partners.
95 members of the inner periphery were identified with the structured interviews

7. The drug-use levels of many core group members were sustained through a
combination of their own income-generating activities (e.g. selling works, stealing,
welfare, panhandling, etc.) and through sharing drugs with members of the inner
periphery who were dependent upon core network members for market information,
purchasing assistance and/or providing a local site to use drugs before leaving the
neighborhood.

8. Members of the 'outer' periphery were defined in this research as drug injectors
who did not inject with core network members.
Members of the outer periphery tended to make their own purchases and use
drugs in the privacy of their homes.
Since they tended not to 'hang out' in the vicinity of local drug markets or drug-using
locations, relatively few ethnographic field observations were made of the outer
periphery.
Although many were recruited for the structured interviews, which were conducted in
the privacy of the research project's storefront, few members of the outer periphery
wanted to talk on the street.