Syphilis
Treponema pallidum subspecies pallidum is a spiral-shaped, Gram-negative bacterium that cannot survive more than a few days outside a human host. Its small genome of 1.14 million base pairs fails to encode the metabolic pathways needed to produce most macronutrients. This biological limitation means the organism relies entirely on its host for survival. The bacterium has a slow doubling time exceeding thirty hours, which complicates rapid detection and treatment efforts. It is highly mobile and possesses an ability to evade the immune system while invading tissues. Humans are the only known natural reservoir for this specific subspecies. Other diseases caused by related Treponema bacteria include yaws, pinta, and nonvenereal endemic syphilis, but these do not cause neurological disease.
Primary syphilis typically appears as a single chancre between one centimeter and two centimeters in diameter about two to six weeks after contact. This firm, painless skin ulceration may be multiple or occur in places other than the genitals. Secondary syphilis follows four to ten weeks later with a diffuse rash involving the palms of hands and soles of feet. Symptoms can also include fever, sore throat, malaise, weight loss, hair loss, and headache. Latent syphilis presents no symptoms yet can last years without treatment. Tertiary syphilis occurs three to fifteen years after infection and includes gummas, neurological problems, or heart symptoms. Without treatment, approximately 15 to 40 percent of people develop tertiary disease characterized by soft tumor-like growths affecting skin, bone, and liver.
Diagnosis usually relies on blood tests because direct visual inspection requires dark field microscopy equipment that many hospitals lack. Nontreponemal tests like VDRL and RPR are used initially but can produce false positives during viral infections or pregnancy. Confirmation requires treponemal tests such as TPHA or FTA-Abs which become positive two to five weeks after initial infection. Dark field microscopy allows immediate diagnosis if performed within ten minutes of acquiring fluid from a chancre. Polymerase chain reaction tests detect specific syphilis genes without requiring living bacteria for analysis. Neurosyphilis is diagnosed by finding high numbers of leukocytes and protein levels in cerebrospinal fluid alongside known infection status.
Elemental mercury was used to treat skin diseases in Europe as early as 1363 before becoming the primary defense against syphilis spread. By the 16th century, mercury preparations sometimes halted disease development when applied to ulcers or inhaled as suffumigation. Medically directed mercury poisoning became widespread through the 17th, 18th, and 19th centuries in Europe, North America, and India. Mercury salts remained prominent medical use as late as 1916 despite being more lethal than the disease itself. The first effective treatment for syphilis was arsphenamine discovered by Sahachiro Hata in 1909 under the trade name Salvarsan. Penicillin was discovered in 1928 and confirmed effective in trials in 1943, making it the main treatment thereafter. Benzathine benzylpenicillin injected into muscle remains the preferred antibiotic for most cases today.
In 2015 about 45.4 million people had syphilis infections with six million new cases recorded globally. During that same year the disease caused approximately 107,000 deaths down from 202,000 in 1990. Sub-Saharan Africa sees rates proportionally higher among intravenous drug users and those infected with HIV. African Americans accounted for almost half of all cases in the United States during 2010. As of 2020 infection rates increased by more than threefold in the US with men comprising 86 percent of all cases. Cuba became the first country to eliminate mother-to-child transmission of syphilis in 2015. Untreated infection carries a mortality rate between eight and 58 percent with greater death rates observed among males.
Paleopathologists have known for decades that treponematosis existed in the Americas before European contact. A 2024 study published in Nature supported syphilis having first emerged among humans in the Americas during the mid-Holocene. Damaged teeth and bones found in medieval skeletal remains provide compelling evidence for pre-Columbian existence. At least fifteen cases of acquired treponematosis based on bone evidence and six examples of congenital treponematosis based on teeth are now widely accepted. Ancient DNA studies remain slow due to the bacterium being rare and fragile in skeletal remains. Research by Marylynn Salmon identified saddle nose deformities often appearing in medieval illuminations especially among men tormenting Christ in crucifixion scenes.
The Tuskegee Study of Untreated Syphilis in the Negro Male ran from 1932 until 1972 involving 600 poor African American sharecroppers from Macon County Alabama. Researchers enrolled 399 men who had contracted syphilis before the study began while 201 did not have the disease. Medical care hot meals and free burial insurance were given to participants but none received penicillin even after it proved successful. The Public Health Service started working on this study in collaboration with Tuskegee University a historically black college in Alabama. Similar experiments carried out in Guatemala from 1946 to 1948 resulted in at least 83 deaths among soldiers prostitutes prisoners and mental patients. An official apology was issued in October 2010 by Secretary of State Hillary Clinton and Health and Human Services Secretary Kathleen Sebelius regarding these ethical violations.
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Common questions
What is the scientific name of the bacterium that causes syphilis?
Treponema pallidum subspecies pallidum is the spiral-shaped, Gram-negative bacterium responsible for syphilis. This organism has a small genome and relies entirely on its human host to survive.
When did primary syphilis symptoms typically appear after contact with the infection?
Primary syphilis typically appears as a single chancre between one centimeter and two centimeters in diameter about two to six weeks after contact. Secondary syphilis follows four to ten weeks later with a diffuse rash involving the palms of hands and soles of feet.
Which treatment was discovered by Sahachiro Hata in 1909 under the trade name Salvarsan?
Arsphenamine was the first effective treatment for syphilis discovered by Sahachiro Hata in 1909 under the trade name Salvarsan. Penicillin was confirmed effective in trials in 1943 and remains the preferred antibiotic today.
How many people had syphilis infections globally in 2015?
In 2015 about 45.4 million people had syphilis infections with six million new cases recorded globally. During that same year the disease caused approximately 107,000 deaths down from 202,000 in 1990.
Where did syphilis first emerge among humans according to a 2024 study published in Nature?
A 2024 study published in Nature supported syphilis having first emerged among humans in the Americas during the mid-Holocene. Damaged teeth and bones found in medieval skeletal remains provide compelling evidence for pre-Columbian existence.
When did the Tuskegee Study of Untreated Syphilis run and how many men were involved?
The Tuskegee Study of Untreated Syphilis in the Negro Male ran from 1932 until 1972 involving 600 poor African American sharecroppers from Macon County Alabama. Researchers enrolled 399 men who had contracted syphilis before the study began while 201 did not have the disease.