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How to: Map sexual networks

Photo: Siegfried Modola/IRIN
Piecing together this sex worker's network
NEW YORK CITY, 30 November 2012 (IRIN) - With whom did you last have sex? When? Where? How? At crowded food stalls and in dimly lit bars, Kelvin Parker carries out what HIV researchers call “sexual networking mapping”.

Networking analysis involves getting intimate details from people who are most at risk of HIV infection to slow the spread of sexually transmitted infections.

Parker, a 48-year-old former prison inmate in the US with a stocky frame and husky laugh, has no academic degrees or knowledge of “fancy math”. But what he does know is how to approach strangers in public places, hang out with them over weeks, gain their trust, and then, talk sex.

A researcher in an upcoming study by Georgia State University on the spread of HIV in Tanzania, Parker said whether in the US or Tanzania, the method is the same: “I’ll talk to anyone and everyone, the same way I always do. I’ll build a rapport with people who gather in places where men have sex with men (MSM). Then I’ll tell people I want to talk to men in this group -and their sexual partners, too - about how they’re connected socially so we can home in on their social networks and work to stop the spread of HIV.”

Parker, who has never done field work overseas before, is part of the small but growing field of sexual network mappers, which explores the spread of sexually transmitted infections (STIs) through socio-geographic factors (such as places, people and practices) instead of looking only at a person’s sexual behaviour independent of community factors.

Experts say this decades-old but rarely used approach could help address - and eventually slow - the spread of STIs. But first, its advocates must overcome stubborn obstacles, such as the extra time and expertise required, as well as concerns of privacy invasion and confidentiality breaches that have prevented sexual network mapping from being more widely utilized until recently.

Targeting at-risk groups

Sexual network mapping identifies and targets groups at high risk of STIs because they frequent a particular place (such as a certain nightclub), belong to a particular at-risk group (such as MSM and sex workers), and/or engage in risky behaviours (injecting drugs and sharing needles with men infected with HIV).

This data collection method started in the late 1970s, when health workers in Colorado Springs, a small city in the western US, were studying the STIs, gonorrhoea and syphilis. “We noticed that some people who were very sexually active never got infected, while others who were less promiscuous contracted disease more frequently,” said John Potterat, an epidemiologist formerly with the US Centres for Disease Control and Prevention who was involved in this early research.

When Potterat and his colleagues started asking people who had STIs about personal behaviours, they made a surprising discovery: of the 300-odd night spots in Colorado Springs, six were associated with half of total infections. “We learned it was geography or where people hooked up that determined their STI risk,” said Potterat.

The Colorado Springs team began doing “contact tracing”, which included asking STI-positive people to reveal the names of their partners in order to find others at risk. Name by name, Potterat and his colleagues mapped out the “network” of people who were transmitting STIs in relation to the town’s six hot spots. Then, they offered safe-sex counselling and pamphlets to people connected to this network - anyone who was having sex with someone attending one of the six night clubs. Over the course of 15 years, they helped lower rates of STI infection by 25 to 40 percent in the city.

This was the same research method that revealed how HIV was spread in the US in the early 1980s through gay men living primarily in San Francisco and New York City. 

Zooming in

Today, “sexual network mapping” and “network-informed methodology” are used as umbrella terms to describe several different forms of STI research: contract tracing of people who test positive for STIs to show how infection started and who is at risk; tracking sexual interaction within communities; tracing behaviours and locations related to STI transmission (called “affiliation mapping”); and doing mathematical modelling based on assumptions such as how many partners subjects have and how infectious an STI is.

These approaches typically involve creating “name trees” - with respondents leading researchers to people with whom they have had sexual contact - or other types of “maps” that identify infectious disease “hotspots”. The goal is to create roadmaps that can direct health workers to people at risk of STIs in order to offer them disease prevention and treatment services.

Supporters of these methods say their biggest advantage is they allow scientists to examine the spread of disease in more detail than commonly used approaches like modelling and projections, which have a higher risk of inaccuracy and offer less detail than network studies.

Photo: IRIN
Trying to reach MSM with condoms
“You can look not just at individual-level characteristics, but at where and when someone appears in a network, how many connections they have to other network members, and how rapidly those connections develop,” said Christopher Hurt, an assistant professor at the University of North Carolina (UNC) School of Medicine who recently published a sexual network mapping study on African-American MSM in North Carolina in the US. 

“You can also look at how disease moves through the network,” added Potterat. “Does it start out slow, then spread quickly? Does it do the reverse? Or just inch steadily along?”

By answering these questions and studying the resulting cartography of disease, researchers can explain why two people may have the same risky behaviour, yet one is much more likely to become infected by a sexually-transmitted disease.

The method identifies at-risk people who would otherwise go undetected, such as the wife of a man who hides the fact he has sex with men in a Dar es Salaam nightclub.

Bringing STI prevention strategies to at-risk network members - identified through interviews - not only saves people’s health and lives, but also ensures limited resources (such as condoms and counsellors) are best used, say health researchers.

“The dream is to capture data in real time and counsel clients based on their predicted risk,” says Hurt. “This could take years to develop, but it’s a very real possibility.”

Confidentiality issue

The downside of sexual network mapping is that compared to alternative methods of study, it requires more time, teamwork and skills, including knowledge of epidemiology as well as applied mathematics (the “fancy math” that Kelvin Parker’s team members do after he provides them with preliminary data).

But even more importantly, it requires absolute confidentiality. Contract tracing, one technique involved, is particularly controversial because it potentially exposes people whose identities are revealed by study subjects, unless researchers are careful to keep names anonymous and replace them with “dummy identifiers” that maintain privacy.

This is one main problem with contact-tracing, said Clifton Cortez, a human-rights trained lawyer who has worked for two decades in HIV response and is now UN Development Programme’s (UNDP) Asia-Pacific practice leader for HIV, Health and Development.

“Violation of people’s confidentiality, especially by health sector workers, occurs so often in most countries… Even if they [researchers] could maintain confidentiality in the research phase, how could they ensure confidentiality would become the norm were such programmes to be more broadly rolled out?”

Such breaches can be fatal for persons exposed to HIV through male-to-male sex, Cortez added, citing homophobia and punitive laws against homosexuals. “Individuals and their families continue to be ostracized, discriminated against, and in extreme cases in some parts of the world, still beaten or murdered because they are HIV-positive.”

Institutional review boards (IRBs, which ensure studies do not harm their subjects) have traditionally frowned on obtaining identities of subjects’ sexual partners without first getting permission from those partners.

“To do this work, you must have your IRB give you a waiver so you can get subjects to identify their partners and get those partners to identify others, too,” said Richard Rothenberg, a public health professor at Georgia State University who will oversee Kelvin Parker’s work in Tanzania.

Before launching field research in Dar es Salaam in February 2013, Rothenberg, Parker and their colleagues must gain approval from three separate IRBs: one in their home state of Georgia, one in neighbouring North Carolina (where their research partner, Family Health International, is located) and the IRB in Tanzania.

In the field, they must find well-established HIV study participant recruiters who can help Parker recruit study subjects.

“Not just anyone can do this type of work,” said Margaret Hellard, an epidemiologist and the director of Melbourne’s Burnet Institute, which in 2011 did a contract-tracing study on HIV in Vientiane, the capital of Laos. “Recruiters asking these questions have to be people with whom subjects can relate. They need to ensure subjects don’t hear about infidelities that could provoke jealousy or retribution. They need to be respectful and careful, never revealing to one subject what another person has said in private.”

Because sexual network mapping studies are so intensive, they typically take two to four years, requiring double the time - and often double the expenses - of other STI field research.

Only about 100 studies that involve some form of sexual network analysis have been published in peer-reviewed, major journals in the past 30 years. Fewer than a dozen of these have drawn what Rothenberg called “complete socio-metric pictures of a sexual group”.

New tools

However, researchers hope new tools will hasten data analysis. “Producing network maps used to be very time-consuming,” said Hurt from UNC. “But new computer software has made graphing much easier.”

Mobile phones and social networking sites (including Facebook) enable researchers to identify, recruit and track network members.

As the Georgia State team gears up for Tanzania and Burnet researchers prepare to bring HIV prevention strategies to Laos, advocates of sexual network mapping say this method holds promise.

“Today, influencing social networks is at the forefront of behaviour change thinking, and better understanding of these [sexual network mapping] tools is increasingly informing the AIDS response,” said Michael Bartos, chief of the Science for Action Division of the Geneva-based Joint UN Programme on HIV/AIDS (UNAIDS).

One hope is that this type of research can help lower HIV infection rates in the populations at greatest risk.

“Why is HIV/AIDS striking hard in certain populations in Africa?” asked the epidemiologist Potterat. “Why is it concentrated in the eastern and southern part of the continent? Network mapping can help us find answers to questions like these - then take steps to stop infection.”

mmg/pt/cb

Theme(s): HIV/AIDS (PlusNews), Aid Policy, Prevention - PlusNews, Stigma/Human Rights/Law - PlusNews,

[This report does not necessarily reflect the views of the United Nations]