1. Syphilis Epidemiology
Thad Zajdowicz, MD, MPH
Medical Director, STD/HIV Program
Chicago Dept of Public Health

2. I am the Medical Director for the STD/HIV Program of the Chicago Department of Public Health. Chicago is dealing with a multi-year outbreak of syphilis. Control of syphilis is possible only through a thorough understanding of its epidemiology, clinical manifestations, and links with other sexually transmitted diseases, such as HIV.

3. Why a lecture on syphilis?
Although syphilis is an eminently treatable
disease, its continuing occurrence illustrates
that our control efforts still need to be
improved. The disease remains elusive clinically
even today, and unless thought of and sought
for can silently cause disease as it has for
centuries. Further, control of syphilis is vital
because of its interactions with HIV. This lecture will focus on syphilis epidemiology; following lectures will explore the clinical manifestations of this most protean of diseases.

4. Objectives To understand the prior and current impact of syphilis
To define current trends of syphilis in the U.S.
To understand how syphilis and HIV interact

5. Etiology and Course
Syphilis is a chronic, systemic infection caused by a spirochete, Treponema pallidum. The primary mode of transmission is via sexual contact. Untreated, syphilis progresses through a primary and secondary stage before becoming latent. Up to 1/3 of people with untreated syphilis develop tertiary disease late in life, primarily cardiovascular and neurologic. Syphilis is also transmitted congenitally from an infected mother to her infant.
See <a href=“ the CDC website</a>

6. Historical Issues Emergence of syphilis in Europe in 1490s
? Imported from the Americas (Columbian theory) or ? Emergence in Europe from other treponematoses
Severe disease (called The Great Pox to distinguish it from smallpox)

7. Pre-Penicillin Era
Highly prevalent in many countries/societies in pre-penicillin era
Estimates of 10% of U.S. population infected in early 20th Century
Higher rates in socially disadvantaged populations, e.g. rural African-Americans in the South
Dramatic drop in incidence/prevalence after introduction of penicillin in mid-1940s

8. Syphilis Worldwide
WHO estimates 12 million new cases of syphilis worldwide (
Greatest burden in adolescents and young adults
Greatest numbers of new cases in South and Southeast Asia, followed by sub-Saharan Africa

9. Syphilis in the U.S. http://www.cdc.gov/std/stats/2002pdf/Syphilis.pdf
The advent of truly effective therapy of syphilis with the introduction and widespread use of penicillin in the 1940s contributed to the great decline of syphilis over the following decades. The rise in the late 1980s and early 1990s coincided with widespread use of crack cocaine and exchange of sex for money and/or drugs. As syphilis rates declined in the U.S. in the late 1990s, the Centers for Disease Control proposed a plan to eliminate syphilis in the United States.

10. Current U.S. Syphilis Epidemiology
Rates of primary and secondary (P&S) syphilis declined every year from
In 2001, rates of P&S syphilis began rising again
However, rise in new cases is seen in men who have sex with men (MSM)
Male:female ratio of cases rose from ~ 1:1 to ~3.5:1 in past 8 years
The male-to-female ratio of P&S syphilis, which had declined from about 3:1 in the early 1980s to approximately 1:1 in the mid 1990s, has once again risen to more than 3:1. This is because syphilis has been substantially curbed in heterosexual populations while it has been resurgent in men who have sex with men (MSM). The reasons for this are not entirely clear, but may involve more risk taking in this group, abandonment of safer sex practices (such as curbing numbers of partners and consistent use of latex condoms), and the rise of a younger cohort of MSM who have no experience with HIV/AIDS from the 1980s, when safer sex practices helped diminish new cases of syphilis and other STDs as a beneficial side effect of reducing HIV transmission.

11. Primary and Secondary Syphilis --- United States, 2002
This figure, from the MMWR of November 21, 2003, shows the changing male-to-female ratios of P&S syphilis in the United States over the past 2 decades. The current syphilis outbreak in the U.S. is largely among urban MSM. CDC noted that 2002 was the 12th consecutive year where P&S syphilis cases declined among women and nonHispanic blacks.
Primary and Secondary Syphilis --- United States, 2002

12. P&S Syphilis Cases by Region
As noted by the CDC, the numbers of P&S cases were highest in the Southeast region in 2002; however, the case count fell from 2001 in the Southeast, and the rate there fell from 3.4 cases/103 to 3.1 cases/103. In the 19 cities reporting more >50 cases, the Southern cities reporting >50 cases each accounted for 39.6% of the total P&S cases in the South for The increasing urban character of syphilis is apparent in these trends.
Primary and Secondary Syphilis --- United States, 2002

13. Race & Ethnicity
In , P&S syphilis rates increased 71.4% among non-Hispanic white men and 28.6% among Hispanic men
No changes in rates in females of same groups
Among non-Hispanic blacks, P&S syphilis rates decreased 10.9%
2.2% for men, 22.6% for women
There were significant rate changes in both Asian/Pacific Islanders and American Indians/Alaska Natives
However, very few cases in both groups overall

14. P&S Syphilis among MSM, Chicago, 2000-2002 by Month of TreatmentCP
Chicago’s recent syphilis outbreak has been primarily in the MSM population. While P&S syphilis cases among MSM had occurred at a constant rate in the late 1990s, the numbers increased after May This was temporally coincident with a large MSM circuit party (a social gathering for thousands of men). One possibility is that increased numbers of anonymous partners during this event may have served as a trigger for the outbreak.
2000
2001
2002

15. P&S Syphilis , by Gender and Sexual Orientation, 1998-2003*, Chicago
*Jan through August
The proportion of P&S syphilis cases in Chicago attributable to MSM rose dramatically beginning in The data here are through August Of interest is the declining proportion of cases among females and heterosexual males. Chicago is representative of other large cities with similar outbreaks.
N=338
N=282
N=292
N=317
N=353
N=161

16. Congenital Syphilis Syphilis is transmissible from mother to infant
Transmission usually occurs during early stages, but may occur at any stage in an untreated mother
Incidence of infection rose in U.S. in late 1980s-early 1990s with rise in heterosexual cases
Congenital syphilis is a systemic infection with profound impact for infected individuals.

17. Congenital Syphilis
Rates of congenital syphilis in U.S. continue to decline as new cases of P&S syphilis decline in heterosexuals
The decline in CS cases is a consequence of interruption of syphilis transmission among heterosexuals. Syphilis prevalence rates in pregnant women in Africa in the 1990s were much higher than in the developed world – 2.5% in Burkina Faso to 17.4% in Cameroon.

18. Epidemiological Synergy
HIV and syphilis co-facilitate transmission of each other
Biological plausible because:
STDs facilitate HIV shedding
Cellular recruitment of HIV susceptible cells occurs
Mucosal barriers are breached
Immunosuppression
Of more than academic interest is the fact that HIV and syphilis co-facilitate each other’s transmission. The reasons are listed on this slide. Estimates from a variety of studies suggest a 2-5 X higher rate of HIV transmission in the presence of ulcerative STDs, such as syphilis. The overall population attributable rate (PAR) of GUD for HIV is estimated at between 7 and 18% in the U.S., and 44 – 69% in the developing world.

19. Behavioral Risk
Behaviors that are risky for transmission of syphilis are also risky for transmission of HIV
This has been demonstrated in studies in various areas of the world
Future lectures will discuss the interactions of syphilis with HIV and why syphilis control is important for both individuals and public health.

20. Sources of Information
The following sites are useful if more
information on syphilis epidemiology is sought:
Centers for Disease Control
World Health Organization
American Social Hygiene Assoc
Virtual Naval Hospital