Epidemiology and Public Health
Carlos Avila
Introduction
This chapter reviews
the epidemiology of the HIV-infection and is focused on public health
programs to prevent the spread of this epidemic in Latin America.
The aim is to review biological, behavioral, and social factors that
significantly impact the course of the HIV epidemic. Also, to review
some important issues in vaccine development from an epidemiological
point of view. Epidemiology is used as a tool to analyze the incidence
and distribution of the HIV-epidemic, to identify risk factors associated
with its spread, and to assess the impact of control interventions.
All this information is processed and directed to decision makers
for the definition of national and regional agendas.
Despite the fact
that AIDS in Latin America has caused more than 80,000 deaths, some
health officials are still hesitant to recognize the importance of
the HIV epidemic as one of the major health problems in our region.
For example, AIDS in Brazil and in Mexico is emerging as the major
cause of death among men between 24 and 45 years of age. In some Latin
American countries, AIDS is only surpassed by injury as cause of death.
Since AIDS affects an important segment of the productive labor force,
the future impact on human capital and on production might be substantial.
Mortality is only one criteria to define priorities in the health
sector. A recently developed indicator combines mortality and disability
caused by disease in one index. Disability Adjusted Life Years (DALYs)
adds the adjusted life years lost due to premature mortality and disability
due to the disease.
Two perspectives
should be taken into account in order to analyze the impact of the
HIV epidemic: its social impact and its burden on the health care
system.
Current status
of the epidemic in Latin America and the Caribbean
HIV-infection
is one of the major cause of mortality and morbidity in developing
as well as newly industrialized countries. In fact, the Joint United
Nations Program on HIV\AIDS (UNAIDS) estimates that 94 percent of
the 21.8 million people living worldwide with HIV\AIDS are in the
developing world. The care and treatment of AIDS patients dramatically
increase the burden on the health systems and divert scarce health-care
resources from preventive care. Given health-care budget constrains,
the allocation of health services strongly depends on the adequate
understanding of the epidemiology of AIDS and HIV infection. The size
of the epidemic in Latin America has major demographic, epidemiological.
and economic implications. As in other regions, the AIDS epidemic
in Latin America and the Caribbean is becoming a major public health
problem. The World Health Organization (WHO) estimates 2 million HIV-infected
people living in Latin America and the Caribbean. Accurate estimation
of the size and velocity of the epidemic would allow planning health
care and social services for HIV-infected people. As of June 1996,
a total of 176,930 AIDS cases have been reported in Latin America.
Nine countries¾ Brazil (71,111), Mexico (26,660), Argentina (6,853),
Colombia (5,763), Venezuela (4,960), Honduras (4,424), Dominican Republic
(2,948), Peru (2,709), and El Salvador (1,248)¾ account for 80 percent
of the reported cases in Latin America. During 1994, the highest cumulative
incidence of AIDS per million population was observed in the Bahamas
(1,183), French Guyana (598), Barbados (458), Guadeloupe (268), Trinidad
(208), Jamaica (142), Honduras (138), Guyana (127), Caiman Islands
(111), Grenada (74), Brazil (75), Panama (72), El Salvador (69), Dominica
(60), Argentina (56), and Mexico (44).
The modes of transmission
vary from country to country. The dominant modes of transmission range
from epidemics that are predominately related to homo-bisexual behaviors,
to epidemics connected to injecting drug use, and to other that are
primarily determined by heterosexual transmission. Sexual transmission
of HIV accounts for 80 percent of overall transmission in the region,
ranging from 64% in Brazil to 90% in Colombia. The AIDS epidemic in
Colombia, Venezuela, and Mexico is mainly homo/bisexual; in Central
America and the Caribbean the epidemic is predominantly heterosexual;
and Argentina and Brazil have an important proportion of IV-drug related
cases.
Sexual behaviors
across the region reflect patterns that place the population at risk
for HIV. These behaviors include early onset of sexual behavior, cultural
acceptability of multiple partners, especially for males, and low
levels of condom use. Tracking trends among individual risk groups
is highly limited in Latin America. A major feature of the AIDS epidemic
in this region is an increasing proportion of AIDS cases with category
of transmission reported as unknown. This emerging category varies
by country and ranges from 13% (Argentina, Chile, Paraguay, Uruguay)
to 50% (Bolivia, Colombia, Ecuador, Peru, and Venezuela).
AIDS cases are
reported to the Regional Program on AIDS/STD, Pan American Health
Organization (PAHO) in Washington. AIDS surveillance remains one of
the main tools for monitoring the course of the epidemic. However,
this information is subject to limitations such as incomplete reporting,
changes in case definitions, and delays in reporting. Reporting delays
may give the false appearance of recent decline in disease when this
decline is due to incomplete reporting of the most recent cases. A
study in Mexico estimated that only 66% of the AIDS cases are reported
within 8 months, 80% within one year, and 91% within 2 years. Under-reporting
of AIDS cases is due to misclassification or failures in the surveillance
system. Several methods for adjustments of under-reporting are available.
The Quebec AIDS surveillance program compared predicted and observed
AIDS deaths and estimated that the completeness of reporting was 92%
in Canada.
Advances in
molecular epidemiology
The identification,
first of HIV-1 and then of HIV-2, and their subtypification using
molecular techniques helped relate these characteristics to the biological
behavior of the virus. While HIV-1 and HIV-2 have apparently distinct
biological properties, the fear of a second HIV-2 epidemic has not
occurred or may be occurring at a lower rate than HIV-1. Follow-up
studies of HIV-infected individuals showed that the rate of AIDS development
is more than 10 times higher in HIV-1 individuals as compared to HIV-2.
Also, HIV-2 is less transmissible compared to HIV-1, by both perinatal
and heterosexual routes. HIV-2 not only appears less virulent than
HIV-1 but also might provide up to 70% protection for subsequent HIV-1
infection. This finding is relevant to investigate mechanisms of immune
development for vaccine research. The variation in the nucleotide
sequence of the envelope gene seems to play an important role in the
pathogenesis of the HIV-1. The inter-patient variation in HIV-1 is
greater than with HIV-2 and this variation correlates with clinical
evidence of immunosuppression. Using quantitative PCR to determine
proviral titer of HIV-infected individuals showed a range of HIV-2
proviral titer 10-to-100 fold lower than of HIV-1, suggesting that
a decreased pathogenesis may be due in part to the lower viral burden.
Recent advances
in the characterization of the HIV-1 genetic subtypes might have major
epidemiological and preventive implications. A phylogenetic classification
system for the HIV-1 is based on the homology of nucleotide sequences
of gag (core) and env (envelope) genes. Changes in the V3-loop are
not captured by the current classification system as a distinct subtype.
This classification system is intended for taxonomic purposes. However,
if this segment of the env is also able to modulate certain biological
behavior of HIV-1 strains, the subtype might also characterize HIV-1
by transmissibility, infectivity, or pathogenesis. Epidemiologically,
the distribution of these viral strains in the population may determine
the course of sub-epidemics within large populations. If proved, this
finding might have implications in understanding the epidemic dynamics,
the development of a vaccine, or to test effective antiretroviral
treatments.
Differentials
in transmission patterns of the AIDS epidemic by geographical region
are traditionally explained by behavioral patterns. A new theory explains
these differences based on genetic differences in the virus circulating
in Asia, Africa, Europe, and the Americas. McCutchan and co-workers
identified five distinct strains of HIV-1: A, B, C, D, and E. There
is a distinctive pattern in the geographic distribution of these strains.
While all the strains are present in Africa, only strain B appears
to be present in the United States. Thai women have been found infected
with strain E and the majority of Indian women are infected with strain
C. These findings may suggest that the Asian epidemics developed by
the spread of E and C strains from Africa to Thailand and India. A
recent report in Science by a Latin American scientist showed
that the E subtypes from Thai heterosexuals grew better in Langerhans
cells than did B strains from U.S. homosexuals(1). Langerhans cells
are found throughout the mucosal linings of the cervix and vagina
and the foreskin of the penis. If demonstrated, this may explain the
hypothesis of a virus with a greater efficiency for heterosexual transmission
which also would explain the geographical patterns of the epidemic.
Assuming that these phenomena exist, then there is an enormous potential
for the introduction of the E and C strains in the Americas where
the predominant subtypes are B, resulting in an explosive heterosexual
epidemic in areas where these subtypes have not penetrated.
The viral monitoring
is very important. The World Health Organization established years
ago an international network for the identification and characterization
of HIV subtypes(2). In Brazil, three different subtypes of HIV-1 have
been reported: B (88.5%), F (8.8%), and C (1.8%). Also, a Brazilian
National Network for HIV-1 Isolation and Characterization has been
established to monitor different HIV subtypes circulating in Brazil(3).
In Mexico, all isolates from 1989 to 1993 showed the B genotype(4),
and confirmed by another study identifying the subtype B in Guadalajara(5).
In Argentina, among 21 HIV-1 samples tested, 14 were subtype B, six
samples subtype F, and one subtype C(6). In Cuba seven samples were
identified as subtype B(7).
In summary, the
new characterization of HIV-1 in subtypes might not only explain the
geographic distribution of the epidemic, but also have important implications
for new sub-epidemics and for vaccine development. Any vaccine in
order to be efficient must induce immunity that recognizes the envelopes
of the different strains. However, one thing should remain clear in
terms of primary prevention: protected intercourse is the best way
to prevent the spread of the HIV regardless of its subtype.
Risk factors
for HIV infection
The definition
of preventive programs is focused on modifiable factors that are associated
with an increased risk of transmission or development of the disease.
In the case of
parenteral transmission, programs of self-exclusion of blood donors,
prohibition of blood commerce and blood-product screening represent
successful programs in the control of the HIV transmission by blood
and blood products. However, improvements are required to achieve
quality control in blood banks and 100 percent safe blood supply in
Latin America. For example, in Sao Paulo, Brazil, there was a report
of nine possible cases of HIV transmission related to blood products(8).
Cases of HIV infection associated to IV-drug use are still under-estimated
in Latin American countries. These cases occurr mainly in urban areas
such as Rio de Janeiro, Brazil(9), Buenos Aires, Argentina(10), and
Mexican cities bordering the United States.
Regardless of
the biological behavior of the virus, today the practice of unprotected
sexual intercourse remains the major risk factor to acquire the HIV
infection. Thus, social networks and behavioral factors outweigh the
biological risks associated with HIV transmissibility. The exchange
of sexual partners and the social networks increase the risk of infection.
Another variable that appears to increase transmission risk is the
co-infection with an STD. High viremia levels are also correlated
with infectiousness which are observed in primary infection and in
late stages of immunodeficiency. Cervical HIV-1 DNA detection is increased
in cervico-vaginal infection, immunosuppression, and with the use
of contraceptives such as injectable progesterone.
The probability
of heterosexual transmission has been estimated from several studies
and seems to be influenced by several factors. For example, at the
beginning of the epidemic in Thailand, the probability of HIV transmission
per sexual act from female sexual worker to men was estimated to be
0.03 to 0.06(11). This estimate is substantially higher than the transmission
risk reported from a multicenter study in Europe of 1.2 per 1,000
unprotected contacts (0.0012), and from estimates in the United StatesS
ranging from 0.0009 to 0.002(12). The higher rate in Thailand could
be explained for many new infected individuals at the beginning of
the epidemic. High levels of HIV viremia are typical of primary HIV
infection which indeed may increase viral shedding and infectiousness.
Mathematical models
are useful to understand the epidemic dynamics and to test the effect
of interventions. Koopman (1996)(13) showed that core groups cause
primary infection to dominate HIV transmission even when more than
90% of virus is excreted during later stages of the infection. Consequently,
vaccines which fail to prevent infection but which reduce or eliminate
contagiousness during primary infection will, in most situations,
stop the HIV epidemic.
Prevention
of perinatal transmission
The spread of
the HIV infection to heterosexual population was followed by an increased
number of infected children due to perinatal transmission. However,
one of the most encouraging areas of prevention is precisely perinatal
transmission.
In Africa, rates
of maternal-fetal transmission have been reported between 35% and
40%; and in the US and Europe from 25% to 30%. The identification
of risk factors has been very useful in designing strategies to prevent
mother-to-child transmission. It is considered that perinatal transmission
is multifactorial. The recognized factors for transmission are divided
into maternal and obstetrical factors. Among the maternal factors,
viral load, the immune status of the mother, her level of CD4 counts,
and the stage of the HIV-infection influence the rate of transmission.
Among the obstetrical factors, breaks in the placental barrier, rupture
of membranes, exposure of the baby to blood, trauma, and type of delivery
are reported as factors that increase the transmission rate. Based
on our current knowledge several questions still remain unanswered,
among others, why does discordant twin infection occur? And why does
selective transmission occur only in about 25% of the infants? Moreover,
currently there are about two dozen pediatric cases with documented
HIV-infection that have been able to clear the infection. Among the
factors that may explain infection rate and progression, viral phenotype
is important; the majority of the virus transmitted is non-syncytium
induced (SI) isolates. The viral load appears to be the most important
but not the only factor associated with the transmission (Fang, 1995).
Based on current knowledge of risk factors, there are three levels
of intervention to reduce the HIV maternal-to-infant transmission.
In-utero transmission is addressed with antiretroviral treatment.
As demonstrated by the AIDS Clinical Trials Group ACTG-076 protocol,
zidovudine administered to the mother reduces transmission in two
thirds, probably by reducing the viral load and the fetus infection.
Inter-partum preventive approaches include vaginal washing, timing
of delivery, and reducing trauma and exposure to cervical secretions.
The model is based on the assumption that cleansing the birth canal
lowered the likelihood of ascending infection. The possible role of
an ascending infection is based on a mechanism thought to contribute
to bacterial (group B streptococcus) and viral infections (herpes
virus). However, a trial using chlorexidine solution at 0.25% failed
to reduce the transmission rate of HIV infection(14) (Biggar, 1996).
Another study showed no effect of C-section, but when practiced with
rupture of membranes of less than four hours the risk of transmission
declined(15). Measures to reduce post-partum HIV-infection rate such
as prophylaxis for the baby and breast feeding are still controversial,
particularly in developing countries.
Currently, the
standard of care includes the administration of zidovudine to all
HIV-infected pregnant women and there are clinical trials testing
the efficacy of other antivirals such as 3TC, protease inhibitors,
and nevirapine. Nutritional factors seem to play a role in the perinatal
HIV transmission. Since deficiency of vitamin A has been associated
with an increased risk of perinatal transmission, clinical trials
of vitamin A supplementation are being conducted in Africa. In summary,
the future for the prevention of perinatal HIV-infection is very optimistic.
Preventive
programs
From a preventive
perspective the HIV epidemic requires sustained mobilization of the
community and expansion of the social response to the epidemic. The
major tasks are to reduce the impact of the epidemic in areas already
affected and to prevent its spread to new areas. There are several
levels of prevention aimed at reducing the occurrence of new infections
as well as the associated morbidity. At the primary level, to prevent
the occurrence of new infections, interventions include the following:
social and behavioral approaches to reduce high-risk practices linked
to the HIV transmission, vaginal virucides for women, consistent use
of condoms, blood and blood-product screening, reduction and treatment
of STDs, antiviral treatment to pregnant women to reduce the perinatal
transmission of HIV, and in the future the use of a preventive vaccine.
Secondary prevention
is aimed at reducing the progression from HIV infection to AIDS and
death. The interventions include timely and more effective antiviral
therapy, reducing psychosocial distress, improving nutrition, and
preventing and treating opportunistic infections.
Activities aimed
at preventing the spread of the HIV-infection have several major components:
(a) input information to elaborate a situation assessment, (b) research,
(c) planning, (d) implementation, and (f) evaluation.
Input information
is essential to guide preventive programs. The bases of this information
are the epidemiological surveillance systems. This system collects
and processes periodic information to monitor the course of the epidemic
and it characterizes the disease in terms of the population more affected,
age groups, geographical location, and category of transmission. The
situation assessment is complemented by sentinel surveys as well as
Rapid Assessment Prevalence Surveys, (RAPS). This method is used by
the Centers for Disease Control to monitor HIV prevalence among high-risk
populations. The HIV tests are conducted by using leftover blood specimens
after removing all identifiers among people attending STDs clinics,
hospitals, women's health centers, and drug treatment centers.
Research is a
major component of any preventive effort. In Latin America, basic,
medical, and social research is required to identify regional particularities
of the epidemic. While some people might think that Latin American
countries lack human resources and facilities to conduct research,
this is only partially true. There are several excellence centers
conducting research. In fact, Brazil is one of the leading Latin American
countries in basic HIV research. Extensive research in HIV-1 and HIV-2
has been conducted, and circulating strains and subtypes are well
characterized. This information is critical for the development of
vaccines and the implementation of clinical trials of available vaccines.
Medical research
is also important to determine patterns of viral resistance to treatments,
regional differences in opportunistic infections, and different prophylactic
and therapeutic approaches.
Social and behavioral
research is essential to determine the distribution of risk behaviors,
social networks, population dynamics, and to identify vulnerable populations.
Planning uses
all available information. A major role in the planning process is
played by the costs as well as the demonstrated effectiveness of the
interventions. Since a strategic plan has to be adjusted to budget
constraints, one criteria to choose investments in programs should
include prioritization and costs-effectiveness analysis. Consensus
building is a major task after planning a preventive strategy and
before its implementation. Of particular importance is to work with
different groups. Since HIV transmission involves sexual practices,
explicit information or certain messages might be sensitive for some
segments of the population.
Program implementation
represents one of the biggest challenges. For example, choosing appropriate
channels to reach the general population for a universal program differs
from a targeted component addressing high-risk populations.
Evaluation should
be part of any intervention. For example, the evaluation of a condom
program has several components; the inputs of the program could be
based on the number of condoms distributed or sold. The process could
be evaluated by assessing the implementation of the program, its coverage,
and ways of delivering it. Outcome evaluation may include impact measurements
such as behavioral change (condom use) or the number of new infections
prevented.
Expectations
for Vaccine-Based Prevention
As in other infectious
diseases one of the most powerful preventive interventions to control
and eventually eradicate the disease relies on the development of
a vaccine. However, any AIDS vaccine is facing several practical problems.
First, extreme optimistic views at the beginning of the epidemic raised
false expectations as to the time when the vaccine would be available
for immediate use in the field. Second, one simple technology will
be unable to stop the epidemic if there is no community mobilization.
Examples of this situation exist for other diseases where, despite
the fact that there is a highly effective vaccine, logistic problems
in the delivery, high costs (in developing countries), adverse reactions,
and public acceptance have limited the vaccine coverage and the eradication
of diseases such as measles, pertussis, tetanus, and polio.
While vaccine
development has high priority, other activities are also needed. It
is necessary to build the infrastructure for clinical trials aimed
at testing new products, their delivery, and costs. These clinical
trials require populations not only with high HIV-incidence, but also
highly motivated to maintain compliance for long term follow-up. Beyond
randomization and control groups, ethical research principles mandate
that all participants receive other preventive interventions to reduce
risk of infection.
Ideally, the new
vaccine should be polyvalent and not only efficacious to subtypes
prevalent in the United States. Seroconvertion and clinical protection
might be complemented with other outcomes such as effect on viral
load and survival. Mathematical models about the dynamics of the HIV-epidemic
show that even a vaccine not 100% efficacious would be able to reduce
the spread of the epidemic substantially. Two major initiatives for
a vaccine development are lead by the World Health Organization and
The International AIDS Vaccine Initiative (IAVI), a non-profit organization
incorporated in January 1996 and sponsored by the Rockefeller Foundation.
The goal of both organizations is to accelerate the development of
a safe and effective preventive vaccine that meets the needs of the
developing world where the burden of infection is centered. These
organizations oppose the development of vaccines only against HIV
subtypes prevalent in the United States and Europe hoping that it
will work in developing countries. Vaccine approaches include: live-attenuated
HIV, nucleic acid, whole-killed HIV and other particles, live recombinant
viral vectors, and live recombinant bacterial vectors.
Lessons of
preventive programs from the world
This section is
aimed at reviewing some of the most relevant reports on preventive
interventions whose efficacy warrants thoughtful analysis and presents
important lessons useful for the public health practitioner.
Impact of
Improved Treatment of STDs on HIV Infection
A growing body
of evidence suggested that ulcerative STDs facilitate HIV transmission.
One of the most compelling evidence of the impact of STD treatment
on HIV infection comes from a randomized trial in Tanzania. The program
lead to a 40% reduction in HIV incidence through the implementation
of a public health STDs prevention and care program(16). The project
improved the diagnosis and treatment of STD's integrated into the
health care center according to guidelines recommended by the WHO.
STD services to
high risk populations such as female sex workers are often provided.
However, as the epidemic affects other groups, adolescents have almost
no access to family planning or STDs services. Condom distribution
at family planning services does not ensure prevention since is not
used by women who follow permanent methods of contraception. One major
problem is the low sensitivity of clinical signs for diagnosis of
STDs. Screening based on risk assessment has only a positive predictive
value of 20% which results in over-treatment of about 80% of treated
women. Health research services in Latin America are required to improve
the current detection, treatment, and delivery of STD to reach different
populations requiring these services.
The 100% Condom
Program in Thailand
The Thai HIV/AIDS
prevention and control program is one of the few programs in the world
with some evidence of success at a national level(17) (Rojanapithayakorn,
1996). The 100% condom program was based on the assumption that the
source of the heterosexual epidemic in Thailand was the commercial
sex industry. The program had two components: (a) it used administrative
means to ensure that condoms were used in commercial sex establishments
at all times (100%) and (b) it launched a mass advertising campaign
promoting the use of condoms in commercial sex. Its national dimension
helps understand the limitations to conduct a reliable evaluation.
Thus, it is not clear which component had the greatest effect or was
more effective. However, impressive results were observed; condom
use increased from 14% before 1989 to over 90% by December 1994. During
the same period, the number of STDs diagnosed in men attending government
clinics declined from 200,000 to 28,000. The program promoted the
use of condoms by commercial sex workers (CSW) and their clients with
no exception. If a consumer refuses, the CSW withholds the service
and refunds the consumer's money. Contact tracing was used to determine
which commercial sex establishment (CSE) was not cooperating with
the program. When a men was diagnosed with an STD, he reported the
CSE were he acquired the infection. A local STD/AIDS unit initiated
a process that led to sanctioning that CSE. To prevent CSE losing
money and, hence, rejection of the program, the local government and
the police were key elements to enforce the observance of the program.
This program offers
several lessons worthy of analysis. National leadership, participation
of the mass media, awareness of the AIDS epidemic, targeted campaigns
for condom use, recognition of the existence of prostitution rather
than disapproving its existence, organization of the sex industry,
use of local STD/AIDS clinics working in a national network, contact
tracing programs, and STDs monitoring as immediate outcome of the
program. While most of these interventions are well known, there are
two other that would require thoughtful analysis because of their
possible limitations for implementation in other countries: law enforcement
and the introduction of economic incentives for CSE.
The AIDS Community
Demonstration Projects in the U.S.
These HIV-intervention
projects began in 1989 targeting high-risk groups in five US cities:
street-recruited injecting-drug users (IDUs); female sex partners
of male IDUs; women who trade sex for money or drugs (female sex traders);
men who have sex with men (MSM) but do not self-identify as homosexual;
and youth in high-risk situations (e.g., street youth who spend most
nights away from home). One of the primary goals of these projects
was to target HIV-interventions to at-risk "hard to reach groups"
populations who were not necessarily participating in established,
facility-based prevention programs. The key components of the project
included: (a) use of behavioral change models and theories to design
the intervention; (b) formative research within the project communities
before the intervention; (c) print materials (e.g., pamphlets, brochures,
flyers) containing stories of persons in the targeted populations
who had changed their HIV-risk behaviors (i.e., role-model stories);
(d) distribution of these materials with condoms and bleach kits by
community networks; and (e) implementation and outcome evaluation.
One interesting element of these intervention projects is that they
incorporated elements of the following theories and models: Health
Belief Model, Theory of Reasoned Action, Social Cognitive Theory,
and Stages of Change (SOC) continuum of the Transtheoretical Model.
The assessment of the intervention showed exposure rates among eligible
respondents ranging from 22% to 68% during the early intervention
phase. Female sex traders were most likely to report exposure to project
materials and staff, while nonhomosexually identifying MSM were the
least likely to report exposure to the intervention program. Behavioral
outcomes for each respondent were measured along the SOC continuum;
stages were coded from 1 (precontemplation), 2 (contemplation), 3
(ready for action), 4 (action), and 5 (maintenance). At the first
stage, an at-risk person may have no intention of changing the high
risk behavior; several events may then lead the person to form intentions
to adopt the behavior in the distant future (contemplation): these
intentions may be followed by initial, perhaps exploratory, attempts
to adopt the behavior (ready for action). The new behavior is then
adopted (action) and ultimately becomes a routine part of the person's
life (maintenance). The outcome objective of the ACDPs was to promote
progress along the SOC continuum toward the goals of consistent use
of condoms and bleach. Progress along these behavioral-change stages
was considered success, although the consistent practice of risk-reduction
behaviors (maintenance) is necessary to prevent transmission of HIV.
For each of four behaviors investigated, the mean SOC value among
persons in the intervention areas who reported exposure to the project
intervention was greater than the mean SOC value among those who did
not report exposure [consistent condom use for vaginal intercourse
with a main partner (2.1 vs 1.9, p<0.05)]. Consistent condom use
for vaginal intercourse with non-main partner was higher in the exposed
group as compared to the non-exposed group (3.1 Vs 2.8, p<0.05);
this was mainly due to a higher proportion of exposed respondents
(41%) than of nonexposed respondents (27%) reporting consistent condom
use. Consistent condom use for anal intercourse with non-main partner
was also higher in the exposed group than in the nonexposed group
(3.8 Vs 2.9, p<0.001) mainly due to a higher proportion of respondents
exposed to the project and reporting consistent condom use for anal
intercourse (58%) as compared with respondents who were not exposed
to the intervention (27%). Consistent use of bleach to clean injection
equipment was also higher in intervention-area respondents exposed
as compared to the nonexposed group (mean SOC 3.3 Vs 2.9, p<0.001).
These results
indicate that persons who are at risk for either sexually transmitted
or needle-borne infections can be favorably influenced toward consistent
risk-reducing behaviors through a community level intervention. To
maximize the influence of the intervention, efforts should be made
to expose as many persons as possible in the intervention communities
to the specific prevention messages.
The revision of
this prevention approach reveals two key elements for the success
of any community program. It was designed to be as sensitive as possible
to the populations concerned and relied on the participation of persons
who were part of that population (peers).
Conclusions
The fight against
the HIV epidemic at this new stage requires three components: recognition,
understanding, and leadership. First, we have to recognize that the
HIV epidemic is an increasing problem across Latin America and the
Caribbean. In this region population dynamics, social networks, and
behavioral patterns are more relevant for the course of the epidemic
than geographical boundaries.
The new knowledge
about the biological behavior of the virus suggests that recognized
subtypes and the biological variability of the HIV has the potential
to induce new waves of subepidemics. To understand epidemic trends,
it is important to make clear that in Latin American countries such
as Brazil and Mexico the deceleration in the overall number of new
reported cases does not reflect the course of the epidemic towards
rural or heterosexual populations. That the hypothesis of a saturation
of the pool of susceptible people, proposed for some North American
cities, is very unlikely to be the case in Latin America. That a population
of 50 million under 15 years living in Latin America will be providing
annually about 10 million adolescents that start sexual activity.
This situation demands an effort to maintain continuous campaigns
to promote safe sex and condom use.
To maintain a
sustained effort to prevent new HIV infections, a strong leadership
is required to promote an international effort to control the epidemic.
This leadership needs to be combined with political will and broad
public consensus that control of the HIV epidemic must be achieved.
There is worldwide agreement that the most pervasive risk factor for
disease in the world today is poverty. Ignorance and poverty are elements
that condition the vulnerability of social groups to suffer epidemics.
Today, a major
leadership and effort to fight against the HIV-epidemic in the Americas
has been conducted by the Pan-American Health Organization. Its main
activity has been to assess the size and course of the epidemic and
provide technical and financial support in the region. More recently,
the Regional Initiative for the Control of HIV/AIDS and other STD's
in Latin America and the Caribbean (SIDALAC) has been launched by
the Fundación Mexicana para la Salud. This new regional initiative
aims at developing research in the HIV arena, that may help decision
makers in their strategic planning for the prevention of the HIV/AIDS
epidemic. Since geographical boundaries will not stop the HIV epidemic,
this leadership is critical to develop partnership for international
preventive efforts.
While governments
are responsible before their peoples for providing adequate access
to preventive and therapeutic care, community involvement and participation
are essential for the success of preventive interventions to control
the HIV-epidemic.
Suggested References
Alcántara R. Prevalence
of STD and HIV/AIDS infection in adolescents that attended service
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