Risk networks, infectious diseases, social norms, risk behaviors and health activism

“intravention” Samuel R Friedman*

Melissa Bolyard

Carey Maslow

Pedro Mateu-Gelabert

Milagros Sandoval

National Development and Research Institutes, Inc., New York, NY

*Friedman is also a Senior Associate, Department of Epidemiology, Bloomberg School of Public Health, Johns Hopkins University

Sunbelt Social Networks Conference, Redondo Beach, California, February 19, 2005 .

Acknowledgements

• This presentation was supported by– NIDA grant R01 DA13128, Networks,

norms and HIV risk among youth – NIMH grant RO1 MH62280 Local

Context, Social Control Actions and HIV Risk

• We want to thank the busy men and women who took part in this study by answering some very personal questions and letting us take specimens.

Background

• Both sexual activity and injection drug use can spread diseases such as HIV, hepatitis B and C, and syphilis.

• The relative probabilities of sexual versus injection transmission varies among these diseases.

• Although STIs such as herpes simplex virus Type 1 (HSV-1) and Type 2 (HSV-2), gonorrhea, and chlamydia seem not to be spread by injection, HSV-1 and HSV-2 seem to be more prevalent among young adult injection drug users (IDUs) than among young adults who do not use “hard” drugs.

• Similarly, men who have sex with men (MSM) tend to be more likely to be infected with many of these disease agents.

Objective

• To study – Ties among IDUs, other drug users, MSM, WSW,

and others.

– how risk network locations are related to:

• infection with various diseases

• vaccination against hepatitis B

• participation in group sex activities

• health activism “intravention”

Methods

Setting

• Bushwick is in Brooklyn, NY.

• Population about 100,000

• Mainly Latino/a, sizeable percent African American

• Impoverished, but beginning to be gentrified

• Many IDUs and other drug users

• Large HIV/AIDS and HCV epidemics centered among IDUs began in 1980s

Sample

• 465 subjects were recruited in 2002 - 2004 in a sexual and injection network serosurvey in Bushwick.

• Links were defined as having injected or had sex with each other, or having attended a groups sex event together, in the prior three months.

• 111 index cases (see next slide)

• 355 subjects were sexual and/or injection partners of 1 or more of the index cases or were partners of such partners or their partners.

• The next slide also shows network ties by gender and drug use.

Index Cases by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

Classification (1)• “Youths” aged < 25 approximately define

those under 18 when youth vaccination against hepatitis B was recommended.

18-24 Year-Olds by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

Classification (2): Core, Sex Partners, and Distance

• Core: Men who have sex with men (MSM) and injection drug users (IDUs) are a core for HIV and HBV infection. n = 230

• Sex partners (SPs) are defined as sex partners of one or more core members. n = 75

• D2 (distance = 2) are sex partners of sex partners. n =26

• D3+ are sex partners of D2 members, or sex partners of other D3+ sex partners. n = 15

• Unlinked are non-core subjects who are not sexually linked to a core group member by a path of any length. n = 119

Blood-borne virus infection by network distance from core

HIV* HCV* HBVª*

Core (MSM &/or IDU) 18% 58% 57%

SPs 7% 6% 26%

D2 0% 0% 13%

D3+ 0% 0% 20%

Unlinked to core 0% 1% 4%

ª HBV exposure among the unvaccinated.

*p chi-sq test for trend) < .001.

Percent testing positive by proximity to core group of IDU or MSM, younger than 25 years

Tested positive

IDU or MSM

(n=26)

Sex partner (n=19)

2+ links

(n=31)

Not linked (n=80)

p-value

p-value

(no core)

HIV 13 0 0 0 .0014 -----

HCV 42 0 0 1 <.0001 -----

HBV 25 17 13 8 .1058 .4852

HSV-2 46 26 17 22 .0344 .8740

Note: Ns may differ due to invalid infection data. Mantel-Haenszel used to compute p-values, unless otherwise noted; asterisk indicates Fisher’s exact test.

Tested positive

IDU or MSM

(n=204)

Sex partner (n=56)

2+ links

(n=10)

Not linked (n=39)

p-value

p-value

(no core)

HIV 19 10 0 0 .0009 .0410

(.1351*)

HCV 60 7 0 0 <.0001 .0784

(.2977*)

HBV 60 27 22 0 <.0001 .0016

HSV-2 62 63 70 58 .8583 .6855

Percent testing positive by proximity to core group of IDU or MSM, 25 + years old

Note: Ns may differ due to invalid infection data. Mantel-Haenszel used to compute p-values, unless otherwise noted; asterisk indicates Fisher’s exact test.

Sexually-transmitted infections by network distance from core

N HSV2* HSV1* Syph.* GC CT

Core (MSM or IDU) 230 60% 85% 5% 1% 6%

SPs 75 53% 86% 3% 1% 5%

D2 26 35% 80% 4% 4% 8%

D3+ 15 21% 71% 0% 0% 36%

Unlinked to core 119 33% 71% 0% 0% 6%

*p (chi-sq test for trend) < .001. N’s differ for infections due to missing data

HIV Positive by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

HCV Positive by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

HBV Status (+=Exposed, V=Vaccinated) by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever

(from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

HSV2 Positive by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

Immunization among 156 youth < 25 years old

• 7% have been exposed to hepatitis B

• Among the 137 “unexposed,” 53% have induced immunity.

• Independent significant predictors of induced immunity:

–Attended church more than once in last year (AOR = 3.73)

–Younger Age (AOR per year 0.80)

Immunization among 166 IDUs aged 25+

• 57% have been exposed to hepatitis B

• Among the 72 “unexposed,” 15% have induced immunity.

As the next slide shows, high-risk communities contain “health activists” who are willing to

urge others to reduce risk behaviors.

• This suggests that efforts might be made to win them to urge others to get vaccinated.

• Outreach methods have been developed to do this for prevention.

• Research is needed to see if vaccine-oriented outreach would be effective in these communities.

Star Urgers by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

Group sex and health activism by proximity to core group of IDU or MSM by age

Mantel-Haenszel p-values, unless

otherwise noted; asterisk indicates

Fisher’s exact test.

IDU or MSM

Sex partner

2+ links

Not linked

p-value p-value

(no core)

<25 years old n=26 n=19 n=31 n=80

Sex at group sex event L12M

46% 21% 32% 14% .0016 .1541

Health activist 38% 21% 13% 6% <.0001 .0435

.0958*

25+ years old n=204 n=56 n=10 n=39

Sex at group sex event L12M

31% 16% 50% 18% .1053 .7169

Health activist 32% 39% 10% 28% .5191 .2236

Sex at Group Sex Party by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

Correlation coefficients with distance from core group

Includes core Excludes core

Pearson r p-value Pearson r p-value

<25 years old

Peers object to high-risk sex (factor scale)

.27 <.0001 -.01 .9020

Peers object to drug use (factor) .35 <.0001 .06 .5634

Peers use drugs (factor scale) -.31 <.0001 -.24 .0127

Number sex partners L3M -.05 .3842 -.09 .3484

25+ years old

Peers object to high-risk sex (factor scale)

.24 .0030 .03 .7256

Peers object to drug use (factor) .41 <.0001 .12 .1894

Peers use drugs (factor scale) -.50 <.0001 -.24 .0065

Number sex partners L3M -.40 <.0001 -.36 <.0001

Conclusions (1): Hepatitis B vaccination rate is low

• Even if we apply Lum’s* young-IDU-based 33% expansion factor on immunization estimates to estimate the rate of completed 3-dose vaccination, many youth have not received their indicated vaccinations.

• Few members of core groups and few of their sex partners (in the 25+ age group) have been immunized.

*AJPH 2003; 93:919-923.

Conclusions (2): Infections

• For HSV-2, IDUs and MSM may be a core group for wider sexual transmission. Among those less than 25 years of age, the virus is concentrated among MSM and IDUs and has lower prevalence with greater network distance from this core. It has become more widespread among those 25 years old or older. Hypothesis: HSV-2 tends to infect IDUs and MSM first among an age cohort, and they operate to an extent as a core group for further spread.

• Risk network position is associated with infection with HIV, hepatitis B, and perhaps HSV-1 and syphilis.

• The probability of current infection with chlamydia and gonorrhea, two curable bacterial infections, is NOT associated with distance from the MSM/IDU core.

Conclusions (3): Sex, norms, and health activism

• Group sex is widespread. It is most common in the core for youth.

• The number of sex partners decreases with distance from the core.

• There are lots of sexual links among MSM and IDUs, and of WSW with both of these groups. This may be one reason why WSW get infected with HIV and other infections.

• The norms of those with closer sexual ties to the core seem to be less protective.

• Health activism (defined in terms of urging others to engage in safer behaviors) is more common in or near the core for youth, suggesting that those at highest risk engage in other-directed prevention efforts.

Question for you

• Given the strong associations of age with network position (and other variables)—which is at least partially methodologically produced by our sampling of so many over-25 IDUs—what are some ways to tease out the connections between network properties and dependent variables like infections, behaviors, and norms?

Chlamydia by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

Cat or Dog as Pet by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

Attended Group Sex Party by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

Unsafe Sex at Group Sex Party by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI

Heroin or Cocaine; blue=other)

HCV/HIV Co-infection by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

HSV2/HCV Co-infection by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

HSV2/HIV Co-infection by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

Urge IDUs to be Safe by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

Urge Others to be Safe by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)

Syphilis Positive by Gender/Sexuality (MSM=up triangle, WSW=down triangle, other female=circle, other male=square) by Hardest Drug Use Ever (from dark red to light pink: IDU, Crack, NI Heroin or Cocaine; blue=other)