World Journal of AIDS, 2013, 3, 357-363
Published Online December 2013 (
Open Access WJA
Prevalence and Incidence of HIV and Sexual Risk
Behaviors in Crack Users in the San Salvador
Metropolitan Area, El Salvador*
Julia Dickson-Gomez1, Julia Lechuga2, Laura Glasman1, Steven Pinkerton1,
Gloria Bodnar3, Pamela Klein1
1Center for AIDS Intervention Research, Department of Psychiatry and Behavioral Medicine, The Medical College of Wisconsin,
Milwaukee, USA; 2University of Texas, El Paso, USA; 3Departamento de Investigación, Fundación Antidrogas de El Salvador
(FUNDASALVA), San Salvador, El Salvador.
Received September 4th, 2013; revised October 4th, 2013; accepted October 11th, 2013
Copyright © 2013 Julia Dickson-Gomez et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Objective: It is in order to estimate the prevalence and incidence of HIV, the frequency of sexual risk behaviors, and
perceptions of available resources to prevent and treat HIV among crack users in the San Salvador Metropolitan Area.
Methods: We conducted a survey of 420 crack users by using respondent-driven sampling to measure demographic
characteristics, the quantity and frequency of drug use, history of STIs, including HIV, and experiences with organiza-
tions which provide prevention and treatment of HIV. Each participant offered a free and voluntary HIV test and was
asked permission to share the results of the test with the study. Bernoullian modeling was used to estimate the preva-
lence and incidence of HIV among heterosexual males in this population. Results: The estimated prevalence was 7%
(95% CI: 2.3% - 9.8%) among participants who agreed to take the test and share the results, and 4.9% (95% CI: 2.8% -
7.8%) assuming that those who did not take the test or share results were seronegative. Participants reported a high fre-
quency of sexual risk behaviors. In addition, participants were reported to have little knowledge of organizations to
prevent or treat HIV/AIDS; 58% had never taken an HIV test prior to survey administration. Conclusions: Crack users
in San Salvador are at high risk for HIV acquisition. HIV prevention interventions are urgently needed, especially in-
terventions increasing access to HIV testing and prevention.
Keywords: Incidence and Prevalence of HIV; Sexual Risk Behavior; Crack; El Salvador
1. Introduction
Non-injection drug use has been associated with high
prevalence of HIV and sexual risk behaviors such as sex
exchanges for drugs or money, sex with multiple partners,
sex without condoms and a high rate of sexual assault
[1-4]. Crack, in particular, has been associated with high
frequency of sex exchanges, lower prices for commercial
sex work, diminished ability to negotiate condoms with
clients and high rates of sexual assault [2,3,5] due in part
to the psychopharmacological effects of crack [5-9]. In
spite of the strong research evidence linking crack use to
HIV risk, crack use is not regularly monitored in surveil-
lance of HIV and few HIV prevention interventions fo-
cus on crack users.
In El Salvador, data on the prevalence of crack use are
sparse. In a national survey conducted in 2004, approxi-
mately 1% of the adult population had used crack in the
past year, reaching a high of 4.9% among 18 years old
people [10]. Among gang members, 65.7% were reported
to use crack in the last month and 25.8% were reported to
use crack daily [11]. A significant number of persons are
affected directly by crack use through their own prob-
lematic use, or indirectly through the effects of drug sales
and use within their communities [12-15].
El Salvador has the second-largest number of people
reported to be living with HIV/AIDS in Central America
[16], with an estimated overall prevalence of 0.8% [17].
*Declaration of conflict of interest: the authors declare that they have
conflicts of interest.
Prevalence and Incidence of HIV and Sexual Risk Behaviors in Crack Users
in the San Salvador Metropolitan Area, El Salvador
However, the HIV epidemic is concentrated among vul-
nerable populations such as men who have sex with men
(MSM; 10.8% prevalence), female sex workers (FSW;
5.7% prevalence) and transgender women (19.7% preva-
lence) [18]. Because the Ministry of Health does not col-
lect data regarding non-injection drug use in national
HIV surveillance data, the prevalence of HIV among
crack users has not yet been estimated.
Through this study of crack users in the metropolitan
area of San Salvador, El Salvador we aim to: 1) identify
the frequency of sexual risk behaviors; and 2) explore
crack users’ knowledge of HIV and available HIV pre-
vention and treatment programs; and 3) estimate the
prevalence and incidence of HIV. The results of this
study will aid in the development of interventions to
prevent HIV transmission among non-injection drug us-
ers in El Salvador and other developing countries.
2. Methods
2.1. Study Population and Recruitment
Surveys were conducted with crack users who lived in
the Metropolitan Area of San Salvador, El Salvador and
were recruited using respondent driven sampling (RDS).
RDS was chosen for the following reasons: 1) RDS has
been shown to be effective in reaching hidden popula-
tions; and 2) With long enough chains of referrals from
seeds, the composition of the sample becomes stable
(reaches equilibrium), and reflective of the universe of
crack users regardless of seed selection [19,20].
Field staff identified and recruited 3 initial “seeds”.
Field staff chose additional seeds when chains of referral
were broken, resulting in a total of 22 total seeds who
recruited 398 survey participants for a total sample size
of 420 participants. Eligibility criteria included residing
in, or using or buying drugs in one of the 7 low-income
communities selected for study, being 16 years old or
older, and having smoked crack in the last 2 weeks. After
completing the survey, seeds were given 3 coupons to
recruit other members of their social network. Eligible
recruits who completed the survey were also given 3
coupons to recruit members of their social networks re-
sulting in several waves of recruitment. Dual incentives
were given to encourage recruitment, $5 for participating
in the survey, and $2 for each participant successfully
recruited into the project.
All participants were read and signed an informed
consent forms in Spanish. The research was approved by
Institutional Review Boards at the Institute for Commu-
nity Research, Hartford CT, the Medical College of Wis-
consin, Milwaukee, WI, and the Universidad Centroa-
mericana Jose Simeon Cañas, San Salvador, El Salvador.
2.2. Survey Measures
Surveys were conducted face to face by trained inter-
viewers and were approximately 90 minutes in duration.
Demographic factors measured included age, gender,
marital status, monthly income, type of employment (for-
mal or informal), and level of education. Participants
self-reported if they worked in the formal or informal
economies. Formal work refers to work that is legally
recognized and from which social security is collected
and other income in paid. Informal work includes both
illegal activities (drug selling, commercial sex work) and
work that would otherwise be legal but which is un-
regulated by any government institution [21,22].
The survey included questions about lifetime sub-
stance use, including alcohol, crack, marijuana, sniffed
cocaine, injected cocaine, sniffed heroin, injected heroin,
nevados (marihuana with cocaine), bañados (marihuana
with crack), and ecstasy. For each substance for which
participant reported use, the participants were asked the
age at which they first started using the substance, and
the frequency and quantity of substance use (number of
days in the last month, number of times in the last month,
and number of times in the day prior to survey admini-
Sexual risk behaviors were measured for the 30 days
prior to survey administration and included the number
of: sexual partners for anal, oral and vaginal sex acts; sex
acts in exchange for money; sex acts in exchange for
crack; sex acts in a location where crack is used; sex acts
with a drug user; and sex acts under the effect of alcohol
or drugs. For each risk behavior, participants were asked
to provide the overall number of sexual partners/acts and
the number of sexual partners/acts without a condom.
Self-reported STI diagnosis history, including the spe-
cific STI diagnosed from a list of common STIs, was also
collected. HIV testing history was also ascertained, in-
cluding whether the participant ever tested for HIV, the
last time the participant took an HIV test in months and
years, and whether they ever received an HIV/AIDS di-
agnosis from a doctor.
Survey participants were asked if they were aware of
organizations that prevented or treated HIV/AIDS or
drug dependence, and whether they had ever received in-
formation, talks or interventions about the prevention or
treatment of HIV or drug dependence. Participants were
asked if they knew of places where they could obtain
condoms, and to indicate the types of places they re-
ceived a condom from a list.
After the survey, all participants were offered a free,
voluntary HIV test. Participants could choose not to take
an HIV test, to take the test and not share the results with
the project, or to take the test and share results with the
project. Staff from FUNDASIDA, a non-governmental
Open Access WJA
Prevalence and Incidence of HIV and Sexual Risk Behaviors in Crack Users
in the San Salvador Metropolitan Area, El Salvador
AIDS Service Organization, administered the test, pre
and post-test counseling. Participants’ decisions regarding
whether to take the test and share results were recorded,
as were test results of participants’ who gave their con-
sent to share results with the project.
2.3. Statistical Analyses
Demographic variables, risk behaviors, substance use,
and knowledge of available services for the prevention
and treatment of HIV/AIDS or substance use were eva-
luated using frequency tables, and means and standard
deviations where appropriate.
HIV prevalence was calculated among all survey par-
ticipants using the Respondent Driven Sampling Analy-
sis Tool 5.6 [23], developed specifically for analyzing
samples recruited through RDS. This analysis program
estimates the prevalence of HIV within a specific popu-
lation (i.e. crack users) based upon percent of persons
living with HIV in the sample, after adjustment for: 1)
the number of crack users with whom the participant
regularly interacted; and 2) the HIV status of the person
who recruited the participant. The RDS network data and
proportional recruitment strategy across groups can then
be used to make unbiased population estimates [19].
HIV incidence rates were estimated among a subsam-
ple of men who reported having heterosexual vaginal or
anal intercourse in the previous month (n = 237). Men
who reported male-male intercourse in addition to het-
erosexual intercourse were excluded from the analyses (n
= 141, 43% of all men). Men with male-male intercourse
were excluded because the survey did not collect infor-
mation on whether participants engaged in receptive or
insertive anal intercourse and these have much different
risks for acquiring HIV.
A Bernoullian model of HIV transmission [24] was
used to estimate each male participants’ monthly risk of
acquiring HIV through vaginal and anal intercourse,
based on the sexual behavior data collected in the main
Monthly risk111ππ11
 
where m is the number of female partners reported by the
participant; k
and k
 are the per-act fe-
male-to-male transmission probabilities for unprotected
and condom-protected intercourse, respectively; ε de-
notes the effectiveness of condoms at reducing HIV
transmission; and π is the prevalence of HIV infection
among the female partners of study participants. This
monthly risk corresponds to an annual risk of
Annual risk = 1 – (1 – Monthly risk)12.
The expected HIV incidence among men in the study
was estimated by calculating the mean annual risk across
study participants.
Values for the number of partners (m) and number of
sex acts with and without condoms (i, j, k, and n) were
drawn from the main study survey. The following values
were assumed for the remaining parameters per-act fe-
male-to-male transmission probability for unprotected
intercourse, k
= 0.0038; and condom effectiveness, ε
= 0.85 [24]. Values for HIV prevalence were obtained
from the estimates calculated as described above. The
average incidence rate for men in the study sample was
calculated together with lower and upper bound esti-
3. Results
Ninety-two percent of the 420 survey participants were
men (n = 386/420). The median age of the participants
was 37.8 years (standard deviation: 9.4; range 18 - 63
years). Most participants reported low levels of educa-
tional attainment; 41% attended primary school, 29.5%
attended some secondary school, and only 21.9% fin-
ished high school. While 83% reported being currently
employed, only 26% were employed in the formal sector
(Table 1).
High levels of alcohol and marihuana use were re-
ported by the survey participants; 99% of participants
Table 1. Demographics.
N %
Age (mean, std dev) 37 9.6
Male 386 92
Female 34 8
Marital Status
Married 67 16
Divorced 164 39
Single 180 43
Monthly Income (mean, median) 252 200
Type of Employment
Formal 109 30
Informal 311 70
Primary School 173 41
Secondary School 124 30
High School 92 18
Post-High School 31 22
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Prevalence and Incidence of HIV and Sexual Risk Behaviors in Crack Users
in the San Salvador Metropolitan Area, El Salvador
Open Access WJA
reported ever using alcohol and 96.4% reported ever us-
ing marihuana (Table 2). After crack, alcohol was the
most frequently used substance (median: 17 days in prior
month). Few participants reported sniffing or injecting
heroin or cocaine and none had reported doing so in the
last 30 days.
Participants reported a high frequency of sexual risk
behaviors in the 30 days prior to survey administration.
On average, survey participants experienced 7 sex acts
without condoms in the last 30 days (Table 3). In the
month prior to survey administration, 28.3% of partici-
pants had sex with 3 or more partners, 13.5% exchanged
sex for crack, 18.5% exchanged sex for money, and
42.4% had sex while under the influence of drugs or al-
Nearly half of participants (49.5%, n = 208/420) re-
ported receiving an STI diagnosis during their lifetimes.
Of those who with a history of STIs, 53.8% were in-
fected with an STI on more than one occasion (n = 112/
208). The most common STI reported by participants
was gonorrhea (30.5%, n = 63/208).
Only 15% participants reported knowledge of organi-
zations that offered HIV prevention programs (n = 63/
420), and 10% knew of organizations to treat HIV (n =
42/420). Of those with knowledge of such organizations,
68.2% reported receipt of information, talks or work-
shops to prevent or treat HIV (n = 43/63). The types of
organizations that offered services were identified as
government organizations (51.1%), non-governmental or-
ganizations (33.3%) and religious organizations (11.1%).
Over half of participants (66.4%) reported obtaining
condoms in the last 6 months; pharmacies (where con-
doms must be bought) and Ministry of Health clinics
(where condoms are free) were the most frequently men-
tioned locations of condom acquisition (Table 4).
Only 42% of participants reported every having had an
HIV test. The most frequently mentioned locations where
HIV tests were received were Ministry of Health clinics
(58.5%). Among participants who had been tested for
HIV, the mean time since their most recent HIV test was
5 months.
Of the 22 RDS seeds, 16 tested negative for HIV and 6
elected not to take the test or share their results. Among
the remaining, non-seed participants, 20 (5%) either self-
reported or tested HIV-positive, 236 (59.1%) tested nega-
tive for HIV, and 142 (35.6%) elected not to take the test
or share their results. Over 50% (54.5%, n = 5/11) of par-
ticipants who self-reported as HIV-positive also reported
receipt of HIV treatment. All participants who reported
or were tested HIV-positive were recruited to our study
by participants who tested HIV-negative. Among those
with a known HIV-test result, the estimated HIV preva-
lence was 7% (90% confidence interval [CI]: 2.3% -
9.8%). If we assumed that those were not tested for HIV
or chose not to share their results were HIV negative, the
estimated prevalence of HIV was 4.9% (90% CI: 2.8% -
HIV incidence rates were estimated for a subsample of
heterosexual male survey participants. The average inci-
dence rate was 0.0022 HIV infections per month (stan-
dard deviation = 0.0034), with a range of 0.000 to 0.0300
HIV infections per month for individual study partici-
pants (Figure 1). The average annual incidence rate was
2.7%. Sensitivity analyses varying the HIV prevalence of
the female partners of the male participants yielded av-
erage incidence rates of 1.6% (π = 2.8%) to 5.2% (π =
4. Discussion
Globally, the use of non-injection drugs, especially crack,
has been associated with high rates of HIV and high risk
Table 2. Quantity and frequency of drug and alcohol use among crack users in San Salvador, El Salvador.
Age First Used Days in Last Month Times in Last Month Times Used Yesterday
N % Median SD Median SD Median SD Median SD
Crack 414 98.6 21 9.06 30 10.98 240 424.8 5 15.62
Alcohol 416 99.0 14 4.75 17 12.06 240 1323.40 4 36.01
Marihuana 405 96.4 15 6.54 3 12.50 6 109.68 0 2.93
Bañados 348 82.9 21 9.91 4 11.72 6 110.02 0 3.47
Sniffed Cocaine 329 21.7 20 7.30 0 6.12 0 19.08 0 0.62
Injected Cocaine 39 9.3 20 8.40 0 0.34 0 0.35 0 0
Sniffed Heroine 32 7.6 22 6.47 0 3.77 0 18.85 0 0.89
Injected Heroine 35 8.3 19 6.75 0 0 0 0 0 0
Note. N = number of participants ever used. % = percentage of participants ever used.
Prevalence and Incidence of HIV and Sexual Risk Behaviors in Crack Users
in the San Salvador Metropolitan Area, El Salvador
Table 3. Frequency of sexual risk behaviors among crack
users in San Salvador, El Salvador in 30 days prior to sur-
vey administration.
Overall Without a Condom
N % N %
Number of unprotected sex acts
0 acts - - 172 40.9
1 - 2 acts - - 35 8.4
3 acts - - 209 50.2
Number of sex partners
0 partners 120 28.6 182 43.3
1 - 2 partners 182 43.3 172 41
3 partners 118 28.1 66 15.7
Sex in exchange for crack
0 acts 351 83.6 365 86.9
1 - 2 acts 12 2.9 7 1.7
3 acts 57 13.6 48 11.4
Sex in exchange for money
0 acts 320 76.2 356 84.8
1 - 2 acts 23 5.5 18 4.3
3 acts 77 18.3 46 11.0
Sex while drunk or high
0 acts 208 49.5 252 60
1 - 2 acts 35 8.3 33 7.9
3 acts 177 42.1 135 32.1
0 0.002 0.004 0.006 0.008 0.01
Figure 1. Distribution of monthly risk of HIV infection
among crack users in the San Salvador metropolitan area,
El Salvador.
sexual behaviors. Despite having one of the largest HIV
epidemics in Central America, the prevalence of HIV and
Table 4. Places where crack users reported obtaining con-
N %
Pharmacy 87 68.6
Supermarket 6 2.2
Gas Station 11 4.0
Store 9 3.2
Government Health Clinic 155 56.0
Private Clinic 14 5.1
Hospital 9 3.2
Mobile Van 9 2.9
NGO 43 15.5
Bar/Brothel 14 5.1
Community Outreach Worker 18 6.5
Friends 58 13.8
Artner 26 9.4
Family 2 1.0
Note. Percentages based only on participants who reported obtaining con-
doms in the last 6 months (N = 279).
high risk sexual behaviors among crack users has not yet
been investigated. To address this gap, we conducted a
survey among crack users in the San Salvador metro-
politan region of El Salvador to assess the frequency of
high risk sexual behaviors, knowledge of and access to
HIV and drug prevention services, and estimate the HIV
prevalence and incidence in this population. Crack users
in San Salvador are at high risk of HIV acquisition due to
sexual behaviors such as sex for money or crack ex-
changes, sex with multiple partners, and sex without con-
doms, as well as the high prevalence of HIV in the popu-
The estimated HIV prevalence among crack users in
San Salvador was 4.9% - 7.0%, which was similar to the
prevalence of HIV among sex workers [18]. In addition
to prevention efforts targeted towards commercial sex
workers, transgender women and men who have sex with
men, prevention interventions must also be developed
and targeted specifically for non-injection drug users.
While many male and female commercial sex workers
also use crack, existing prevention efforts will not work
for all crack users, particularly those who do not identify
as sex workers because they pay for, rather than are paid
for, sex exchanges, or because they exchange sex on a
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Prevalence and Incidence of HIV and Sexual Risk Behaviors in Crack Users
in the San Salvador Metropolitan Area, El Salvador
sporadic basis [25,26]. Based on mathematical modeling
and our respondent driven sample design, the average
annual HIV incidence among heterosexual males was
estimated to be 2.7%, which suggests that failing to in-
tervene with this population could cause an alarming
increase in the incidence of HIV/AIDS. In scenarios with
higher rates of HIV prevalence in female partners of het-
erosexual males, the annual average incidence could be
as high as 5.2%.
Knowledge of and access to HIV prevention and treat-
ment resources among non-injection drug users in El
Salvador was low. Over half of participants had never
before been tested for HIV. Very few participants were
aware of organizations that worked to prevention HIV
(15%) or offered HIV treatment (10%) in their communi-
ties. This low level of awareness of HIV prevention and
treatment resources may explain the low prevalence of
HIV testing among this population.
Future research should examine whether the lack of
knowledge regarding specific organizations that treat
HIV/AIDS in the community is related to a general lack
of knowledge of the existence of free and effective HIV
treatment. In-depth interviews with substance-using peo-
ple living with HIV in El Salvador revealed that many
persons had no knowledge of antiretroviral therapy be-
fore their diagnosis, received little information about the
importance of linking into medical care, and still be-
lieved that HIV was a death sentence (publication forth-
coming). While improved HIV counseling and testing
may increase the proportion of substance using persons
living with HIV who link to medical treatment, many
non-injection drug users may still be reluctant to test for
HIV unless general knowledge of effective treatments is
Access to condoms in the San Salvador Metropolitan
Area was inadequate; only 66.4% of participants reported
that they had bought or obtained condoms. Most often,
participants reported buying condoms from businesses.
However, a high percentage also reported obtaining free
condoms from government health clinics. Importantly,
few participants received condoms through community
outreach workers. Community outreach might reduce
barriers to obtaining condoms related to stigma (condoms
must be requested from Ministry of Health clinics) and
affordability [26]. In turn, improved access may increase
condom use in this population.
Crack users reported high rates of risky sexual behav-
iors. In the month prior to survey administration, over
half of the participants reported having had sex without a
condom on more than 3 occasions; 28.3% had more than
one sexual partner, and 16.4% exchanged sex for crack
or money. Over half reported having been diagnosed
with an STI in the last year, putting them at even greater
risk for becoming infected with HIV [27-29]. Efforts to
increase timely STI screening and treatment in places
that are accessible and acceptable to crack users, e.g.
clinics, soup kitchens or shelters, may reduce the risk of
HIV transmission.
The majority of survey variables—except for the re-
sults of HIV tests—was self-reported and could have
been influenced by social desirability bias. However, a
survey that resulted in self-reported measures was the
most viable way to access sexual and drug use behavior
data on this traditionally hidden and stigmatized popula-
tion. In spite of our efforts to recruit female crack users,
nearly all survey participants were male, which limits the
generalizability of our results. Further, due to the small
numbers of female crack users, HIV incidence could only
be estimated for males.
5. Conclusion
Crack users are at especially high risk for HIV acquisi-
tion. However, national surveillance in El Salvador ne-
glects to monitor this key and vulnerable population. Our
study addresses this important knowledge gap, estimating
HIV prevalence and incidence among crack users in San
Salvador. Given their high rates of risky sexual behavior
and drug use, as well as lack of knowledge of available
HIV prevention and treatment options, crack users in San
Salvador are especially vulnerable to acquisition of HIV
and other STIs. Improved surveillance and prevention
efforts tailored to the needs of this high risk population
are needed to mitigate the HIV and drug use epidemics in
San Salvador.
6. Acknowledgements
We wish to thank the FUNDASALVA research team,
without whom this study could not have been possible,
and the support of the Universidad Jose Simeón Cañas de
El Salvador. This Project was funded by the National
Institutes of Health (R01 DA020350 and P30 MH57226).
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