Curable versus incurable STDs

1
Curable versus incurable STDs
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Objectives

• To describe the natural history and epidemiology
  of two curable STDs (i.e. syphilis and
  chlamydia) and two non-curable STDs (i.e. Herpes
  and HPV)
• To discuss study design issues specific to
  curable versus non-curable diseases

3
Natural history of a curable disease
Symptoms
diagnosis
cure
Infection
Testing
treatment
Prevalence ? (incidence cured)
4
Things that contribute to non-treatment among
curable STDs

• Lack of index treatment
• Failure to return for treatment
• Non-adherence to medication
• Given incorrect medicine
• Lack of partner treatment
• Treatment failure

5
Natural history of a non-curable disease
Symptoms
diagnosis
Infection
Testing
Prevalence ? incidence
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Non-curable STDs (e.g. HIV, Herpes, HPV)

• Long infectious period
• Few population based screening programs
• No curative treatments
• Incidence may be very different than prevalence

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Treponema pallidum (syphilis)
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Issues in syphilis

• Test doesnt tell if it is incident and wont
  pick up tertiary
• Symptoms change depending on staging
• Most at risk, least likely to get tested and
  treated

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Syphilis - curable

• Caused by Treponema pallidum
• primary lesion usually occurs 3 weeks after
  exposure
• secondary manifestations occur weeks to 12 months
  after initial exposure
• tertiary
• treatment is parenteral penicillin G

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Progression of syphilis
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Staging of Syphilis
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Testing and symptoms
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Male chancres
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Chancre in a female
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Late stage manifestations of syphilis
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ChlamydiaSexually Transmitted Disease
Surveillance 2001

• Division of STD Prevention

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Chlamydia Number of states that require
reporting of Chlamydia trachomatis infections
United States, 19872001
18
Chlamydia Reported rates United States,
19842001
19
Chlamydia Rates by state United States and
outlying areas, 2001
Note The total rate of chlamydia for the United
States and outlying areas (including Guam, Puerto
Rico and Virgin Islands) was 275.5 per 100,000
population.
20
Chlamydia Rates by region United States,
19842001
21
Chlamydia Rates by sex United States,
19842001
22
Chlamydia Age- and sex-specific rates United
States, 2001
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Chlamydia Positivity among 15-24 year old women
tested in family planning clinics by state
United States and outlying areas, 2001
Note States reported chlamydia positivity data
on at least 500 women aged 15-24 years screened
during 2001. SOURCE Regional Infertility
Prevention Program Office of Population Affairs
Local and State STD Control Programs Centers for
Disease Control and Prevention
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Tests

• Culture
• antigen detection (indirect)
• nucleic acid amplification (direct)

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Herpes
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Issues for Herpes

• Variable presentation
• Stigma and reporting bias
• Non-treatable
• Prevalence increases with age

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Herpes Simplex -2

• One of most common, 1 million incident and 45
  million prevalent in U.S. per year.
• Less than 10 of those infected are aware.
• Greek term meaning to creep or crawl
• Acquired sexually
• HSV-1 (oral herpes) can cause 30-40 of genital
  herpes
• Tested using an antibody test
• Increasing age, low SES, more partners, women and
  African Americans at higher risk

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HSV-2

• More than 20 of Americans are infected
• From 70s to 90s prevalence increased 30
• NHANES suggests it leveled off in 1990s except
  for white teenagers.
• Treated with acyclovir, famciclovir,
  valaciclovir, foscarnet, cidofovir gel,
  trifluridine and interferon
• an effective therapeutic vaccine for genital
  herpes has not been successful to date, although
  a live virus glycoprotein H-deficient (DISC)
  vaccine is currently in clinical trials

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Genital herpes Initial visits to physicians
offices United States, 19662001
SOURCE National Disease and Therapeutic Index
(IMS America, Ltd.)
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Genital herpes simplex virus type 2 infections
Percent seroprevalence according to age in
NHANES II (1976-1980) and NHANES III (1988-1994)
Note Bars indicate 95 confidence
intervals. National Health and Nutrition
Examination Survey
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Complicated Scenarios

• How to measure incidence of HIV?
• How to study the efficacy of a vaccine for
  Herpes?
• How to study the efficacy of treatment for HPV?