Download Methods for Studying curable versus non

Behavioral Research and STIs
Objectives
 Discuss how behavior influences the
basic reproductive rate of an epidemic
 Describe some of the behavioral models
 Discuss the concept of Core Group
 Discuss Social Network Analysis
Behavioral versus Clinical
Clinical
 Bioavailability of
medication
 Resistance
 Other physiologic
factors
 Timing of treatment
 Partner treatment
Behavioral
 Characteristics of
sexual partners
 Characteristics of
sex
 Characteristics of
health seeking
 Social influence
Basic Reproductive Rate of
Infection
Ro=  D c
Ro
is the basic reproductive rate of
infection

is the transmission coefficient
D
is the infection periods
c
is the mean rate of sexual partner
change
The Reproductive Rate
Ro > 1
epidemic
Ro = 1
equilibrium
Ro < 1
prevalence
declines
Ro basic reproductive rate
Defines the average number of
secondary infections generated by one
primary case in a susceptible population
of defined density
 the host population is divided into
compartments: susceptibles, infected
(latent), and infectious

()Transmission Probability
infected and susceptible
 number of partners
 types of partners
 types of sexual acts
 frequency of sexual acts
 virulence of infection
 duration of infection
 when infection occurred
 when infection was treated

Sexual Risk Behavior (Aral, 194)
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Age at sexual debut
Number of sex partners
Non-discriminating sex partner recruitment
Sexual practices
Frequency of intercourse
Intercourse during menses
Condom use
Vaginal douching
Male circumcision
Behavioral Models of Disease
Trait Concept
Antisocial personality
 Chronic self-destructiveness
 Erotophobia-erotophilia
 Impulsivity
 Independence-conformity
 Locus of control
 Masculinity-femininity
 Neuroticism-extraversion-psychoticism

Trait Concept
Risk taking
 Self-efficacy
 Self-esteem
 Self-monitoring
 Sensation seeking
 Sex guilt
 Social desirability


 is some constant transmission probability per sexual
act. Possion process is therefore 1 – exp(- n)
Assumption is that this probability is constant, independent
and random.
However, is is more likely that  varies according to sexual
act and the distributional properties of and correlation
between different types of sexual behavior.
Studies of HIV, fail to show a clear relationship between the
number of sex acts per unit of time between infected and
susceptible persons and the liklihood of transmission
D - the Infectious Period
infectousness varies in duration and intensity
Ro = c D (1 t 1 +2 t 2 + 3 t 3)
1 t 1 determines the initial rate at which the
epidemic increases and Ro determines the
total size of the epidemic
c - mean rate of sexual
partner change
depends on demographic and social
factors
 magnitudes are correlated with other
factors such as number of sex acts, type
of sexual contacts and mixing.
 Does a Core Group exist?

Core Group
Core Group
(Thomas and Tucker, 1996)
Defined as:
People who infected a large proportion
of the time, infect more than one other
person, are repeatedly infected, are
prostitutes or their clients, geographic
areas with large numbers of cases
 Mathematical
 Clinical-epidemiologic
 sociocultural

Definitions applied to Core Group
(Thomas and Tucker, 1996)
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Groups whose prevalence of GC is > 20%
Prostitutes
Persons who have many sexual contacts
very sexually active persons who are asymptomatic
when infectious
people repeated infected with STD
people with > 5 sex partners
people with clusters of high-risk behavior
adolescent males in detention
census tracts that are responsible for > 50% of cases
Social Network Analysis
Linear Concept of
transmission of an STD
Network informed concept of
disease transmission
Sexual Behaviors
(Aral; 1994)
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Early age at sexual debut
Large number of lifetime sexual partners
Large number of current sexual partners
Non-discriminating sex partner recruitment
patterns
High risk characteristics of sexual partners
Specific sexual practices
frequency and timing of sexual intercourse
Sexual abuse during childhood
Health Behaviors
(Aral; 1994)
Condom and Contraceptive use
 Vaginal douching
 Male circumcision
 Health Care seeking
 Compliance with therapy
 Compliance with behavioral
recommendations

Substance Abuse
(Aral; 1994)
Associated with anonymous sex
 Associated with exchange for drugs or
money
 Reduces likelihood that safer sex will be
practiced
 Includes injectables, inhalables, and
alcohol

Transmission Process
Shiboski and Padian, JID 1996;174
Partner choice
population/
group
level factors
sexual contact
Transmission
individual/
Partner
level factors