Syphilis is a bacterial infection caused by the bacterium Treponema pallidum. It is spread primarily though sexual contact, however the infection can also be passed from mother to fetus during pregnancy or childbirth, causing congenital syphilis in the infected offspring. Syphilis is unique among sexually transmitted infections (STIs) in that its symptoms vary dramatically depending on the individual's stage of infection. Once a life-threatening infection, syphilis' symptoms have become much more manageable in modern times due to the widespread availability of medical treatments and the decreasing capability of the Treponema pallidum virus to invade host tissues and cause disease.


If left untreated, syphilis will progress through four stages of infection: 1) primary, 2) secondary, 3) latent, and 4) tertiary or late stage. Each stage is characterized by a shift in the presentation of the infection's symptoms.

Stage One: The Primary Stage

The primary stage is the first to occur and is typically acquired from direct contact with another individual's infectious lesions. Primary symptoms include:

  • Appearance of a single, firm, usually painless, non-itchy skin ulceration called a “chancre.” The chancre typically appears three to 90 days after exposure to the bacterium.

  • Appearance of multiple chancres. This is more commonly observed in patients who are also infected with HIV as these conditions tend to exacerbate each other.

(Primary extragenital chancre on left index finger.)

Stage Two

The secondary stage of syphilis typically occurs four to ten weeks following the primary infection and can last as long as one year Secondary syphilis is known to manifest in a wide array of different symptoms, including:

  • A red-pink non-itchy rash covering the hands and feet and eventually spreading across the entire body

  • Muscle aches

  • Fever

  • Sore throat

  • Swollen lymph nodes

  • Wart-like sores inside of the mouth and/or in and around the genital region

Stage Three: The Latent Stage

If secondary syphilis is not treated, the infection will progress to a completely asymptomatic stage called the latent stage. The latent stage may last for years, and symptoms may never return or the disease can progress to its final and most harmful stage. The latent and tertiary stages of syphilis are not transmissible.

(Red papules and nodules covering the body of an individual with secondary syphilis)

Stage Four: The Tertiary or Late Stage

The tertiary stage of syphilis affects 15 to 30 percent of people with syphilis who do not receive treatment. Usually occurring years after the initial infection, tertiary syphilis is life-threatening. At this stage, the disease is not infectious and can include the following symptoms:

  • Formation of chronic gummas (soft, tumor-like balls of inflammation) in the liver, on the skin or bones

  • Syphilitic meningitis

  • Poor balance

  • Pain in lower extremities

  • Seizure

  • Dementia

  • Blindness/deafness

  • Aneurism

  • General apathy, resulting from syphilitic meningitis

Congenital Syphilis

In addition to the typical staged progression of syphilis, congenital syphilis (syphilis passed from mother to child during pregnancy or childbirth) manifests in a separately unique fashion. Infants with congenital syphilis do not typically have symptoms at first, but the disease may progress to include a rash, deafness, teeth deformities, and collapse of the bridge of the nose.


Causes and Risk Factors

Syphilis is caused by Treponema pallidum, a gram-negative spirochete bacterium whose only natural hosts are human beings. Approximately 30 to 60 percent of those exposed to primary or secondary syphilis will contract the disease. It can be transmitted through sexual contact, childbirth, and blood products, as well as kissing the area near a lesion. Syphilis cannot be contracted from toilet seats, bathtubs, clothing, eating utensils, doorknobs, swimming pools or hot tubs. Increased risk factors for contracting syphilis include:

1) Engaging in unprotected sex.

2) Having sex with multiple partners. Multiple partners increases the likelihood that one of them is a carrier of the disease

3) Being a male who has sex with other males. Unprotected anal sex is the riskiest form of sex and the most likely to transmit an STI

4) Having HIV. Compromised immune system increases one's risk of contracting infection

Histopathology of Treponema pallidum bacterium.


Syphilis can naturally either resolve itself (and remain in an indefinite latent stage) or it can progress to the tertiary stage of infection, often resulting in death if left untreated. Eight to 58 percent of untreated cases of syphilis result in the death of the infected individual. Few complications result if the infection is treated in its early stages.

Secondary syphilis affecting the male genitals.


Syphilis can often be hard to diagnose in its earlier stages due to the numerous symptoms that are common among a number of other conditions. This infection is typically diagnosed by testing samples of blood, fluid from sores, and/or cerebrospinal fluid.

Blood tests can confirm an important symptom of syphilis: the presence of particular antibodies that the body produces to fight infection. The antibodies that target syphilis-causing bacteria remain in your body for years, so a blood test can be used to determine a current or past infection. In addition, a doctor may scrape a small sample of cells from a sore and have them analyzed by microscope in a lab. This test can only be performed during primary or secondary syphilis, when sores are present. The scraping can reveal the presence of bacteria that cause syphilis. If it is suspected that an individual has any nervous system complications resulting from syphilis, his or her doctor may also suggest collecting a sample of cerebrospinal fluid through a procedure called a lumbar puncture (or “spinal tap”). Despite the accuracy of these methods, such diagnostic tests are unable to differentiate between different stages of syphilis. This excludes the sore fluid method which must be performed on an individual with primary or secondary stage infection, though this test cannot distinguish between the two stages.

A 1936 poster encouraging the public to get tested for syphilis.


Methods of treatment differ significantly depending on whether the individual has early- or late-stage syphilis. For early infections (less than one year), the favorable treatment would be a single dose of intramuscular penicillin G or an oral dose of azithromycin. Alternatively, doxycycline or tetracycline might be used, but they are not preferred by pregnant females due to the health risks they pose to the fetus. Syphilis has been observed to develop resistance to certain antibiotics, including clindamycin and rifampin.

Late-stage syphilis involving infection of the nervous system is typically treated with very heavy doses of intravenous penicillin for a minimum of 10 days. If the infected individual is allergic to penicillin, ceftriaxone may be used instead. Other late presentations of syphilis may be treated with weekly administration of intramuscular penicillin G for a duration of three weeks. Treatment of late-stage syphilis limits any further progression of the illness, but does little to ameliorate the damage that has already occurred.

The first day of treatment might be accompanied by a day-long condition known as the Jarisch-Herxheimer reaction; symptoms of the Jarisch-Herxheimer reaction include fever, chills, nausea, achy pain, headache, and tachycardia. These side effects usually start an hour after treatment begins and are caused by cytokines (signaling proteins) released by the immune system in response to compounds left from rupturing bacteria.

After treatment, patients are typically asked to have periodic blood tests to ensure a continued appropriate response to the usual dosage of penicillin. Patients are also advised to avoid sexual contact with others until the completion of treatment and blood tests verify the absence of infection. It is suggested that patients also be tested for the HIV infection.


Being diagnosed with an STI is certainly a traumatic experience. One might be angry if one feels they have been betrayed by his or her sex partner or ashamed if there is a chance that they infected others. At its worst, syphilis can cause chronic illness and death, even with the best and most up-to-date care in the world. Between such extremes is a host of other potential losses, including trust between partners, plans to have children, and the untroubled joy of your sexuality and sexual expression.

In order to cope with the extraordinarily stressful situation of fighting an STI, one should follow these guidelines:

  • Do not immediately blame your partner for the infection. One or both of you might have unknowingly been infected by a previous partner.

  • Be honest with health care workers. They are there to help you – not to judge you. Any misinformation could halt the progress of your recovery and treatment.

  • Contact your local health department. They may not have the staff and funds to offer especially comprehensive services, but they likely maintain STI programs that provide confidential testing, treatment and partner services.


Prevention of syphilis is relatively commonsense. Abstinence or monogamy are primarily the first two best options for avoiding the syphilis infection. Using a latex condom can also reduce one's risk of contracting syphilis, but this is only so if the condom covers the syphilitic sores. Avoiding recreational drugs is also advised, as these may cloud one's judgment and lead to unsafe sexual activities. People recently infected with syphilis are often unaware that the infection has even occurred. In light of the fatal effects syphilis can have on unborn children, health officials recommend that all pregnant women be screened for the infection.

(Wearing a condom during sexual intercourse greatly reduces one's risk of contracting a sexually transmitted infection)

Prevalence and Statistics

Rates of syphilis infection have been increasing over the past three decades with approximately 36,000 new cases reported every year. Ninety percent of cases occur in developing nations. The infection affects between 700,000 and 1.6 million pregnancies a year, resulting in spontaneous abortions, stillbirths, and congenital syphilis. Syphilis increases the risk of HIV transmission by two or five times and co-infection (infection by both viruses) is common with rates of 30-60% in certain urban centers. If left untreated, syphilis has a mortality rate of 8% to 58% with a greater death rate in males. The symptoms of syphilis have become less severe throughout the 19th and 20th centuries partly due to widespread availability of effective treatment and decreasing virulence of the bacterium. Rates in the United States are currently six times greater in men than women and seven times greater in African Americans than Caucasians. More than 60% of cases in the United States are among males who have sex with other males, occurring most commonly for males ages 15 to 40 years old.


Mayo Clinic staff. Syphilis. Mayo Clinic. 14 Dec, 2010.

Secondary syphilis: the classical triad of skin rash, mucosal ulceration and lymphadenopathy. International Journal of STD & AIDS. 21 (8): pp. 537–45. Aug 2010.

Syphilis - CDC Fact Sheet. Centers for Disease Control and Prevention (CDC). Web. 16 Sep 2010.

Trends in Reportable Sexually Transmitted Diseases in the United States, 2007. Centers for Disease Control and Prevention. Web. 2007.


Image resources


Last updated 14 May 2014.