Syphilis is a bacterial infection caused by Treponema pallidum – a spiral organism identified by its motility under a microscope. The incubation period for the infection (ie, time from initial exposure to development of infection) varies from 10 to 90 days, with an average of about three weeks.

Syphilis is also classified as an ulcerative STI because the infection causes sores or open lesions mainly on external genitals, anus, vagina or lips. The infection is passed when a noninfected person comes into contact with a lesion, usually during sexual activity such as vaginal, anal or oral sex.

Once the bacteria enter the skin – usually through minute cuts or abrasions – the bacteria multiply locally and then spread to lymph nodes. The risk of getting infected over a certain period of time through sexual transmission from an infected to an uninfected person is roughly 30 – 60%.1 

Pregnant women can also pass it to their babies through the placenta. Such transmission can result in stillbirth or severe deformities in the newborn.2

What are the Stages of Syphilis?

Syphilis is a systemic disease that can affect various systems in the body and can last a lifetime. The disease progresses through four distinct phases:
Latent (early & late)

What is Primary Syphilis?

•Single sore (chancre), there could be multiple too
•Firm, round, painless; indicates point of bacterial entry
•Typically occurs on genital skin and mucosa
•May also occur in mouth, hands, or other parts of body
•Heals by itself in 3-6 weeks
The primary lesion of syphilis is a chancre or a single sore. The sore is the result of bacterial replication at the site of entry and usually occurs on genital skin or on the lips. The sore however, may also be seen on other parts of the body that have come into contact with infected lesions. It is usually painless although it may be accompanied by enlargement of local lymph nodes. Even if untreated, the sore heals in a few weeks. Because the chancre usually is painless and heals by itself, many people do not seek treatment and the disease progresses to the next stage.
What is Secondary Syphilis?
•Symptoms are caused by the spread of the bacteria
Fever, sore throat, rash, lymph gland swelling, loss of hair1
•External genital lesions called condyloma lata
•Lesions resolve in 3-12 weeks2
As the bacteria spread through the body, an illness occurs that is characterized by mild fever, body aches, a typical rash (seen in nearly 75-100% patients, especially on palms and soles1), and lymph node enlargement. It may also be accompanied by a loss of hair. Condyloma lata are raised, moist, painless external lesions that may appear where two surfaces of skin rub against each other — such as the groin. These are not typical ulcers like chancres; they are highly infectious. Due to the widespread infection, symptoms of inflammation of joints, liver, kidneys, stomach, or the nervous system may also occur during this stage. The symptoms of secondary syphilis may resolve after a few weeks or months without therapy, and the disease enters a latent stage.1,2

1.1. Augenbraun M. Syphilis and the Nonvenereal Treponematoses. In: Dale DC, ed. Infectious Diseases: The clinical guide to diagnosis, treatment, and prevention. New York: WebMD. 2003:416-435.
2.2. Stamm LV. Biology of Treponema pallidum. In: Holmes et al., eds. Sexually Transmitted Diseases. New York: McGraw Hill. 1999:467-485.

What is Latent Syphilis?
•Latent stage can be divided into early and late stages
•Mostly asymptomatic and contagious
•Early latent stage usually during first year of infection
•One-fourth of patients in early latent stage have a relapse (ie, become symptomatic again)
•In late latent syphilis relapse is rare
•May resolve by itself or advance to the tertiary stage1

In latent syphilis patient is asymptomatic but has positive tests for antibodies against syphilis bacteria. This stage is often arbitrarily divided into early and late stages.

During early latent syphilis, approximately one fourth of patients relapse or go back into a symptomatic stage. During late latent syphilis, relapse is rare, and patients are immune to new infections.

While there may be no symptoms of the disease during latency, bacteria keeps damaging internal organs. Such damage appears in the form of the late symptoms of syphilis. Latent syphilis usually resolves by itself or advances to the tertiary stage after a year or so.1
1.1. Musher DM. Early Syphilis. In: Holmes et al., eds. Sexually Transmitted Diseases. New York: McGraw Hill. 1999:479-485.

What is Tertiary Syphilis?

•Occurs in one-third of the cases, months or years after latency1
•Causes walls of major arteries to weaken and balloon out; these aneurysms can rupture and may be fatal
•Affects the brain and its coverings to cause paralysis, mental confusion, insomnia and headaches
•Gummas or destructive lesions in skin, bones, and other organs2
Based on the famous Oslo study that was conducted at the end of the nineteenth century, we know that about a third of the cases of secondary syphilis progress to the late or tertiary stage in the absence of any treatment.1 It is estimated that of those who develop tertiary syphilis, about a half have benign late syphilis, a quarter have symptoms of the heart and blood vessel involvement, and a quarter have neurologic disease.2
The cardiovascular symptoms of tertiary syphilis usually appear after many years of a latent stage and men are affected more often than women. It involves the major blood vessels coming out of the heart (aorta) and those supplying heart muscles (coronary). The involvement of the central nervous system may be severe and cause inflammation of the coverings of the brain (meningitis). It may also cause delusions, loss of memory, and seizures.
Occasionally, late syphilis is characterized by destructive inflammatory lesions – gummas – of the skin, bones, or other organs. The gummas of skin and bones are usually benign, but those in the brain, spinal cord, or covering of the heart may have serious effects.2 

Syphilis is most common in the South (CDC, 1997).

Syphilis can cause serious birth defects.

1.1. Augenbraun M. Syphilis and the nonvenereal Tre[onematoses. In: Dale DC, ed. Infectious Diseases: The clinical guide to diagnosis, treatment, and prevention. New York: WebMD. 2003:416-435.
2.2. Swartz MN, Healy BP, Musher DM. Late syphilis. In: Holmes et al., eds. Sexually Transmitted Diseases. New York: McGraw Hill. 1999:487-509.

[from The Medical Institute,]

Syphilis, Primary and Secondary

In 2004, rates of primary and secondary syphilis increased for the fourth consecutive year to the highest level (2.7 cases per 100,000 population) reported in the United States since 1997 (1). These increases occurred only among men; however, for the first time in >10 years, the rate of primary and secondary syphilis among women did not decrease but remained essentially unchanged from 2003. Rates increased among both black and white men. CDC is collaborating with partners from throughout the United States to revise the Syphilis Elimination Plan for 2005–2010 (2).

CDC, Primary and secondary syphilis—United States, 2003–2004. MMWR 2006;55:269–73.
CDC. Sexually transmitted disease surveillance, 2004. Atlanta, GA: U.S. Department of Health and Human Services, CDC. Available at
[CDC, MMWR, June 16, 2006 / 53(53);1-79 Summary of Notifiable Diseases — United States, 2004]