This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike License. Your use of this
material constitutes acceptance of that license and the conditions of use of materials on this site.
Copyright 2007, The Johns Hopkins University and Jonathan Zenilman. All rights reserved. Use of these materials
permitted only in accordance with license rights granted. Materials provided “AS IS”; no representations or
warranties provided. User assumes all responsibility for use, and all liability related thereto, and must independently
review all materials for accuracy and efficacy. May contain materials owned by others. User is responsible for
obtaining permissions for use from third parties as needed.
Epidemiologic Basis of STD Control: Introduction
and STD Surveillance
Jonathan Zenilman, MD
Johns Hopkins University
Section A
Background on STDs
STDs: Background
„
„
„
„
„
15 million cases annually in the U.S.
Predominantly adolescents and young adults
Major cause of Morbidity and Mortality in developed and developing
countries
Other issues—women’s health, child health, association with HIV
Stigma
4
Sexual Health
„
Sexual health is a state of physical, emotional, mental, and social
wellbeing in relation to sexuality; it is not merely the absence of
disease, dysfunction, or infirmity. Sexual health needs a positive
and respectful approach to sexuality and sexual relationships, and
the possibility of having pleasurable and safe sexual experiences
that are free of coercion,discrimination, and violence. For sexual
health to be attained and maintained, the sexual rights of all
individuals must be respected, protected, and satisfied.
5
Overview of Complications of STDs
6
Combined Frequency of Infection of Four Curable STIs:
Gonorrhea, Chlamydia, Syphilis, and Trichomonas
Source: Figure 3. Glasier A, et al. Sexual and reproductive health: a matter of
life and death. Lancet 2006;368(9547):1595-1607. Copyright © 2006 Elsevier
Ltd. All Rights Reserved.
7
Events and Outcomes: Costs and Morbidity of Sexual Behavior
„
„
„
„
„
„
„
Unintended pregnancy
Low birth weight infants
Terminations
STD direct costs-medical (PID)
Long-term STD costs (ectopics, infertility)
Emotional and economic costs
Potentiated HIV risk (three to six times the risk)
8
The IOM Report of 1997: The Hidden Epidemic
„
“Despite the tremendous health and economic burden of STDs, the
scope and impact of the STD epidemic are underappreciated and the
STD epidemic is largely hidden from public discourse. Public
awareness and knowledge regarding STDs are dangerously low, but
there has not been a comprehensive national public education
campaign to address this deficiency.”
9
Section B
STD Surveillance: General Principles
Assessment
„
Systematically collect, assemble, analyze, and make available
information on the health of the community, including statistics on
health status, community health needs, and epidemiological and
other studies of health problems
Source: Institute of Medicine, 1988
11
Disease Surveillance: Objectives
„
„
„
„
Determine trends of incidence and prevalence
Provide strategic direction to disease prevention and medical care
programs
Provide baseline data for evaluation
Identify “sentinel” events for public health action
12
Disease Reporting Issues: STDs
„
„
„
„
„
„
Public/private biases
Classification of contacts
Case definitions—syndromic treatment
Resource availability
Funding stream
Timeliness
13
STD Surveillance Challenges
„
„
„
„
„
Identify the appropriate outcomes/measurements
Prevalent vs. incident disease
Do you have to count every case?
Clinical/syndromic case definitions
Variable needs in different areas
14
Incubation Periods
„
„
„
„
„
„
Gonorrhea—days
Chlamydia—weeks
HPV—three to six months
HIV—three to six weeks
Syphilis—three to six weeks
Trichomonas—days
15
Incident STDs
„
„
„
„
„
Typically bacterial infections which are curable
Short incubation period
Often symptomatic
Susceptible to reinfection after treatment
Examples—gonorrhea, syphilis, chancroid
16
Estimated Burden of STIs in Society
Source: Figure 4. Glasier A, et al. Sexual and reproductive health: a matter of life and death. Lancet
2006;368(9547):1595-1607. Copyright © 2006 Elsevier Ltd. All Rights Reserved.
17
“Prevalent” STDs
„
„
„
„
„
Usually chronic viral infections
Incident infection difficult to detect
Cross-sectional studies identify prevalent disease, usually with
specific serology assays
Often long latency period
Examples—HIV, herpes simplex, CMV
18
HSV-2 Seroprevalence in the United States
Prevalence (%)
25
20
15
10
5
0
1978
1990
2000
AW-245 8-13-1996.
Source: Fleming, P. (1997), NEJM; CDC National Meeting, 2004
19
Prevalent Infections: The Control Challenge
„
„
„
„
Strategy based on prevalent data
Time trajectory often not known
Evaluation of interventions is methodologically difficult
Use of surrogate (e.g., behavioral) markers for evaluation
20
Section C
Syphilis—STD Reflecting Social Trends
Primary and Secondary Syphilis Rates: U.S., 1970–2004
and the Healthy People 2010 Target
Rate (per 100,000 population)
25
P&S Syphilis
2010 Target
20
15
10
5
0
1970
73
76
79
82
85
88
91
94
Note: The Healthy People 2010 target for P&S syphilis is 0.2 case per 100,000 population
97
2000
03
22
Primary and Secondary Syphilis (Rates by Race/
Ethnicity): U.S., 1962–2005
Figure 32. STD Surveillance 2005. CDC
23
Syphilis in the U.S.: 1940s
24
Syphilis in the U.S.: 1940s
25
Primary and Secondary Syphilis (Rates by State): U.S.
and Outlying Areas, 1998
0.8
0.0
0.1
0.0
0.2
0.2
0.2
1.2
0.1
0.2
0.2
0.5
0.9
0.3
4.1
3.6
0.5
3.0
0.8
3.7
1.2
0.2
2.0
2.2
2.7
9.7
10.6
4.3
7.2
Guam 0.0
9.6
6.3
4.4
2.3
9.9
0.2
VT
NH
MA
RI
CT
NJ
DE
MD
0.8
0.2
0.9
0.7
2.2
2.0
Rate per 100,0
population
<=4
4.1-8
>8
0.3
Puerto Rico 4.6
Note: The total rate of primary and secondary syphilis for the United States and outlying
areas (including Guam, Puerto Rico and Virgin Islands) was 2.6 per 100,000 population. The
Healthy People year 2000 objective is 4.0 per 100,000 population.
STD Surveillence 2002. CDC
Virgin Is. 6.4
26
Primary and Secondary Syphilis (Rates by State): U.S.
and Outlying Areas, 2005
Figure 29. STD Surveillance 2005. CDC
27
Primary and Secondary Syphilis (Cases by Reporting
Source and Sex): U.S.,1996–2005
Figure 31. STD Surveillance 2005. CDC
28
Primary and Secondary Syphilis (Male-to-Female Rate
Ratios): U.S., 1981–2004
Male-Female rate ratio
10:1
8:1
6:1
4:1
2:1
0
1981
83
STD Surveillance 2004. CDC
85
87
89
91
93
95
97
99
2001
03
29
Incidence of Total Syphilis in 2005 by Province
Numbers in parentheses show number of provinces in band
Figure 4. Chen et al. Syphilis in China: results of a national surveillance programme. Lancet 2007;369:132-138
30
Section D
GIS as an Applied Tool
GIS Application: The Baltimore Syphilis Epidemic
„
„
„
In 1997-1999 there was a large syphilis epidemic in Baltimore
GIS mapping was used to describe the outbreak
The outbreak was characterized by endemic and “spread” areas
32
Pathways of STD
„
“Every time someone in Baltimore comes to a public clinic for
treatment of syphilis or gonorrhea, John Zenilman plugs his or her
address into his computer, so that the case shows up as a little
black star on a map of the city. It's rather like a medical version of
the maps police departments put up on their walls, with pins
marking where crimes have occurred. On Zenilman's map the
neighborhoods of East and West Baltimore, on either side of the
downtown core, tend to be thick with black stars. From those two
spots, the cases radiate outward along the two central roadways
that happen to cut through both neighborhoods. In the summer,
when the incidence of sexually transmitted disease is highest, the
clusters of black stars on the roads leading out of East and West
Baltimore become thick with cases. The disease is on the move. But
in the winter months, the map changes. When the weather turns
cold, and the people of East and West Baltimore are much more
likely to stay at home, away from the bars and clubs and street
corners where sexual transactions are made, the stars in each
neighborhood fade away.”
33
Reported Primary and Secondary Syphilis Rates by
Year: 1995-2004 (Projection)
100.0
90.0
Rate per 100,000
80.0
70.0
60.0
50.0
Baltimore
US
40.0
30.0
20.0
10.0
0.0
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004*
* Projected 2004 rate;
2003 and 2004 U.S. are rates unavailable
Source: Baltimore City Health Department, STD Surveillance Unit (July, 2004)
34
1994
35
1995
36
1996
37
1997
38
1998
39
1999
40
2000
41
2001
42
2002
43
Gonorrhea (Rates by Race and Ethnicity): U.S., 1981–
2002 and the Healthy People 2010 Objective
Rate (per 100,000 population)
2,500
White
Black
Hispanic
Asian/Pac Isl
Am Ind/AK Nat
2010 Objective
2,000
1,500
1,000
500
0
1981
83
85
87
89
91
93
95
97
99
2001
44
Gonorrhea (Rates by State): U.S. and Outlying Areas, 2005
Figure 29. STD Surveillance 2005. CDC
45
Defining Population Based STD Prevalence in Baltimore
„
„
„
Health department reports are biased towards symptomatic disease
cases seeking care
Private sector/public sector reporting bias
Development of new nucleic acid based tests (NAATS)—Gaydos,
Quinn; facilitate population assessments
46
Geographic Distribution of STDs
„
„
„
„
STDs are not equally distributed across neighborhoods
Studies in Colorado Springs, Dade County, North Carolina, Miami,
San Francisco, and Baltimore show similar findings
Development of mapping and GIS tools have facilitated this area of
study
Most governments now have active GIS units
47
Gonorrhea Rate Categories by Census Block Group in
Baltimore, MD, 1995–1998
= GC 5,000-1,039 per 100,000
= GC 1,038–167 per 100,000
= GC 166-0 per 100,000
48
Gonorrhea Rate Per 100,000 by Census Block Group in
Baltimore, MD, 1994–1999
49
Prevalence of STDs in Baltimore?
„
What is the true population prevalence of STDs in Baltimore?
Charles F. Turner; Susan M. Rogers; Heather G. Miller; William C. Miller;
James N. Gribble; James R. Chromy; Peter A. Leone; Phillip C. Cooley;
Thomas C. Quinn; Jonathan M. Zenilman. Untreated Gonococcal and
Chlamydial Infection in a Probability Sample of Adults. JAMA 2002 287:
726-733
OBJECTIVE: To estimate the overall prevalence of untreated gonococcal
and chlamydial infections and to describe patterns of infection within
specific demographic subgroups of the young adult population in
Baltimore, Md.
50
Probability Sample of Baltimore City Adults
„
„
„
„
„
„
1,014 adults 18-35
Probability sample of residences from tax rolls
Random selection within household
45 minute survey + LCR testing
Crude response rate—71%
Oversamples—white CTs with high STDs, males in black CTs
51
Weighted Estimates (Standard Error) of GC/CT
Prevalence in Baltimore, 1997-1998
Disease
Chlamydia
Gender
Black
White
Female
6.4 (2.2)
0
Male
1.1 (0.7)
2.4 (1.3)
Female
9.3 (3.3)
1.3 (0.5)
Male
5.3 (2.0)
1.3 (0.5)
Gonorrhea
Source: Turner C, et al. Untreated Gonococcal and Chlamydial Infection in a Probability Sample of Adults. JAMA
2002 287: 726-733
52
Citywide Estimates: Gonorrhea
„
„
„
4,566 cases reported in 1998 (2.6% prevalence)
Survey self reported estimate: 4,708 (2.7%) - 5,231 (3.0%)
NAAT-positive at time of survey—9,241 persons infected (5.3%)
53
Policy Conclusions
„
„
„
„
„
An estimated 7.5-8.3% of the population 18-35 has untreated GC or
CT
Nearly all infections were asymptomatic
Prevalence is greater than three times that estimated from
Baltimore City Health Department statistics
Baltimore likely represents a “best case” for STD surveillance data
reporting
RTI colleagues funded for second surveillance study
54
Section E
Chlamydia Surveillance Issues
“Cross-Over STDs”
„
Chlamydia and trichomonas
− Both curable
− May be asymptomatic for prolonged periods of time
− Have epidemiological characteristics of incident and prevalent
infection
− There are large surveillance and control programs in place for
chlamydia due to large scale support for testing
56
Chlamydia (Rates by Sex): United States, 1984–2003
Rate (per 100,000 population)
500
400
300
Men
Women
200
100
0
1984
86
88
Source: STD Surveillance 2003. CDC.
90
92
94
96
98
2000
02
57
Chlamydia (Rates by County): United States (2003)
Rate per 100,000
population
<=150.0
(N= 1,498)
150.1-300.0 (N= 939)
>300.0
Source: STD Surveillance 2003. CDC.
(N= 703)
58
Outcome Measurements: Disease
„
„
Acute
− Gonorrhea/chlamydia
− Pelvic inflammatory disease
− HPV
Chronic
− Infertility
− Ectopic pregnancy
− Cervical cancer
− (HIV)
59
Section F
STD Surveillance-Operational Issues
Sources of Surveillance STD Data
„
„
„
„
„
Health department data
Community surveys
National databases
Hospital databases
Payor data (Medicaid, etc.)
61
Pelvic Inflammatory Disease: Hospitalization of Women
15 to 44 Years of Age: U.S., 1996–2004
Note: The relative standard error for these estimates of the total number of acute
unspecified PID cases range from 8% to 11%.
62
STD Surveillance Data Flow
Provider
County or City
Health Dept
State Health
Dept
Lab
ESS
MMWR
Other
Publications
CDC Data
Warehouse
63
Reporting Structure of China’s Nationwide STD
Surveillance System
64
STD Behavioral Surveillance
„
„
„
„
„
New issue
Need for baseline data
Identification of high risk groups for intervention
Validity/reliability issues
Objective—assess intervention effectiveness and secular behavioral
trends
65
Sources of Behavioral Surveillance Data
„
„
„
Qualitative surveys
Population-specific—STD clinics, jails
Cross sectional
− Telephone surveys (BRFSS)
− Face to face surveys (NHANES)
− ACasi
66
Bias Issues
„
„
„
„
Population selection
− YRBSS
− Population specific
− Response differential
Phone surveys have major selection issues because of technology
Ascertainment bias
Reporting bias
67
Sexual Behavior Events
„
„
„
„
„
Age of sexual debut
Numbers of partners—serial/concurrent
Condom use patterns
HIV risk profiles
Other co-morbidities
− Drug use, economic impact, commercial sex, travel
68
Structural Influences on Behavior and STI Risk
„
„
„
„
„
„
„
„
Status of women
Migration (internal and external)
Gender ratio (e.g., China, Baltimore)
Age at marriage
Religious/social norms
External stress (e.g. war, conflict)
Economic issues (Macro and Micro)
Public health efforts
− Behavioral
− Clinical
69
Condom Use at Last Sex: GSS
70
60
50
40
Regular
Casual/New
30
20
10
0
1996
1998
2000
2002
Source: Adapted from Anderson JE, et al. Changes in HIV-Related Preventive Behavior in the US Population:
Data From National Surveys, 1987–2002 (2003), JAIDS; 34: 195-202
70
Male Condom Use at Last Sex with a Non-Regular
(Non-Marital, Non-Cohabiting) Partner
71
Percentage of High School Students Currently Sexually
Active* by Sex and Race/Ethnicity** (2005)
100
Percent
80
60
47.4
40
33.9
34.6
33.3
32.0
Total
Female
Male
White
35.0
20
0
Black
Hispanic
* Had sexual intercourse with ≥ 1 persons during the 3 months preceding the survey
** B > W, H
Source: National Youth Risk Behavior Survey (2005). CDC
72
Percentage of High School Students Who Were
Currently Sexually Active* (1991–2005)
100
Percent
80
60
40
37.5
37.5
37.9
1991
1993
1995
34.8
36.3
1997
1999
33.4
34.3
33.91
2001
2003
2005
20
0
* Had sexual intercourse with ≥ 1 persons during the three months preceding the survey
1
Significant linear decrease, P < .05
Source: National Youth Risk Behavior Surveys (1991–2005). CDC
73
High School Students Who Used a Condom During Last
Sexual Intercourse* by Sex** and Race/Ethnicity*** (2005)
100
80
70.0
Percent
62.8
68.9
62.6
57.7
55.9
60
40
20
0
Total
Female
Male
White
Black
Hispanic
* Among the 33.9% of students nationwide who had sexual intercourse with one or more persons during the three months
preceding the survey
** M > F
*** B > W > H
Source: National Youth Risk Behavior Survey (2005). CDC.
74
Percentage of High School Students Who Used a
Condom During Last Sexual Intercourse* (1991–2005)
100
Percent
80
60
52.8
54.4
1993
1995
56.8
58.0
57.9
1997
1999
2001
63.0
62.81
2003
2005
46.2
40
20
0
1991
* Among students who had sexual intercourse with one or more persons during the three months preceding the survey
1
Significant linear increase, P < .05
Source: National Youth Risk Behavior Surveys, 1991–2005. CDC.
75
Section G
STD Surveillance-Specific Populations
STD Surveillance-Specific Populations: Determining
Disease Prevalence
„
„
„
Population-based survey methods
− Statistical (NHANES) vs. convenience samples (GISP)
New diagnostic methods for clinical and population-based surveys
− Urine STD diagnostics—LCR/PCR
− Oral HIV tests
Serial serological surveys
77
National Surveys: STD/HIV as Outcomes
„
„
„
„
Not part of surveys until 1988
Surveys since have included mostly STD self-report
Biological measures in NHANES (HSV, RPRs), NSAM (urine for GC,
chlamydia)
Recent advances include urine tests for GC, chlamydia, saliva HIV
tests, self-administered vaginal swabs
78
Military STD Surveillance Issues
„
„
„
„
„
At-risk population
Mobile population
Universal health care access
Interaction with communities
Interaction with other servicemen/women
79
Surveillance and Managed Care
„
„
„
„
Movement of traditional STD populations into managed care
(Medicaid)
Role of public health laboratories
MCO model often not oriented to disease surveillance
Syndromic patient management
80
Antimicrobial Resistance Surveillance
„
„
„
„
A need for standardized susceptibility determinations (MIC from
culture)
Developed multicenter approach in 1986
Adopted in EU, Asia, Australia
Collect behavioral and biological data
81
Principles of GISP
„
„
„
„
Standardized lab procedures including Q/A
Standardized reagents
Resistance definitions and clinical action thresholds
Systematic collection of isolates (first 25 males in participating
clinics)
82
Laboratory-Based Surveillance
„
„
„
„
Resistance tracking
Plasmid or subtype analysis
Confirmation of clinical algorithms
Confirmation of surveillance definitions
83
Gonococcal Isolate Surveillance Project (GISP): Location of
Participating Clinics and Regional Laboratories: U.S., 2003
Seattle
Portland
Minneapolis
Salt Lake City
Chicago Cleveland
Denver
San Francisco
Las Vegas
Detroit
Philadelphia
Baltimore
Cincinnati
St.Louis
Los Angeles Long Beach
Orange Co.
Albuquerque
San Diego Phoenix
Greensboro
Oklahoma City
Birmingham
Atlanta
Dallas
New Orleans
Anchorage
Tripler AMC
Honolulu
Gonococcal Isolate Surveillance Project (GISP). CDC.
STD Clinics
Clinics and
Regional Labs
Miami
84
GISP: Neisseria Gonorrhea Isolates with Resistance or
Intermediate Resistance to Ciprofloxacin, 1990–2003
Percent
7.5
Resistance
6.0
Intermediate resistance
4.5
3.0
1.5
0.0
1990
91
92
93
94
95
96
97
98
99
2000
01
Note: Resistant isolates have ciprofloxacin MICs ≥ μg/ml. Isolates with intermediate resistance have
ciprofloxacin MICs of 0.125–0.5 μg/ml. Susceptibility to ciprofloxacin was first measured in GISP in
1990. GISP 2004 Surveillance Supplement. CDC.
02
03
85
Conclusions
„
„
„
„
Trend analysis is critical for effective STD surveillance
Focused/sentinel STD surveillance approaches are cheaper and
easier
New diagnostic test technology facilitates field activities
Core group approaches may be warranted
86