“The French disease” is an old name for syphilis, a sexually transmitted bacterial infection that has been known by dozens of names since it first devastated Europe in the late 1400s. The term originated as a blame game: Italians called it “the French disease” after French troops spread the infection across Italy in 1495. The French, naturally, called it “the Neapolitan disease” and pointed the finger right back.
Why Every Country Blamed Its Neighbors
Syphilis carried enormous stigma from the very beginning, and no nation wanted to claim it. The naming pattern followed political rivalries almost perfectly. Italians, Germans, and the English called it “the French disease.” Russians called it “the Polish disease.” The Polish called it “the German disease.” The Danish, Portuguese, and North Africans called it “the Spanish disease.” The Turks called it “the Christian disease.” Each population pointed at whoever they liked least.
The name “French disease” stuck more than the others, largely because of timing. In 1494, King Charles VIII of France invaded Italy with a massive army. By 1495, syphilis was tearing through those troops, and an Italian physician named Alessandro Benedetti became the first doctor to formally document the disease while treating soldiers at the Battle of Fornovo. The association with French soldiers became permanent in the popular imagination.
Where Syphilis Actually Came From
The true origin of syphilis is still debated. The traditional theory holds that Columbus and his crew brought the bacterium back from the Americas in 1493, just before the French invasion of Italy. The timing fits neatly. But a growing body of evidence complicates this story. Skeletal remains from across Europe show bone lesions consistent with syphilis, some possibly dating to the 14th century, well before Columbus sailed. DNA analysis published in Current Biology identified strains of the bacterium with a dating range reaching back to the early-to-mid 1400s, potentially before any contact with the Americas. The diversity of strains found around that period suggests the pathogen had already established itself in Europe, since that kind of genetic diversity takes time to evolve.
What likely happened in the 1490s, regardless of origin, was an explosive spread fueled by war, mass troop movements, and the sexual behavior common in military campaigns. The early pandemic form of syphilis was far more violent than modern cases. During its first hundred years in Europe, the disease caused extreme suffering, inspiring authors and poets to write about their agony. Only later did it settle into the slower, staged progression recognized today.
What Syphilis Actually Does to the Body
Syphilis is caused by a corkscrew-shaped bacterium called Treponema pallidum. It spreads through oral, vaginal, and anal sex, through contact with infectious sores on areas not covered by a condom, and from mother to child during pregnancy. Transmission typically happens during the first two years of infection, when sores and rashes are most likely to be present.
The disease progresses through distinct stages, each with different symptoms:
In the primary stage, one or more sores appear at the site where the bacterium entered the body. These sores are typically firm, round, and painless, which means many people never notice them. They last three to six weeks and heal on their own, with or without treatment. This self-healing is deceptive because the infection is still active.
The secondary stage brings skin rashes, often on the palms of the hands or soles of the feet. These rashes tend to be rough, reddish-brown, and faint enough that some people overlook them entirely. Other symptoms can include fever, swollen lymph nodes, sore throat, patchy hair loss, headaches, weight loss, and deep fatigue. These symptoms also disappear on their own, which again creates a false sense of recovery.
After that comes the latent stage, a long quiet period with no visible symptoms at all. Without treatment, the bacterium can remain in the body for years or even decades. Most people with untreated syphilis stay in this stage. But for some, the infection eventually progresses to the tertiary stage, which can appear 10 to 30 years after the original infection. At this point, the disease attacks internal organs, including the heart, blood vessels, brain, and nervous system. Tertiary syphilis can cause memory loss, personality changes, dementia, blindness, hearing loss, and death.
At any stage, syphilis can also spread to the brain, eyes, or ears. Brain involvement can cause severe headaches, confusion, muscle weakness, and cognitive decline. Eye involvement can cause pain, redness, vision changes, or blindness. Ear involvement can produce hearing loss, ringing in the ears, and vertigo.
Historical Treatments and Their Costs
For centuries, the primary treatment for syphilis was mercury, applied as ointments, inhaled as vapor, or swallowed as pills. The phrase “a night with Venus, a lifetime with Mercury” became a dark joke across Europe. Mercury did sometimes suppress symptoms, but it also poisoned patients. Mercury toxicity causes nerve damage, kidney failure, tooth loss, and severe pain that can mimic the very symptoms of late-stage syphilis. The case of Danish author Karen Blixen illustrates this perfectly: she contracted syphilis in 1914, took mercury pills for a year, and suffered severe mercury poisoning. Researchers later argued that her lifelong neurological symptoms were more likely caused by the treatment than by the disease itself.
Arsenic-based treatments replaced mercury in the early 1900s, and bismuth compounds followed. None were safe or reliably effective. It wasn’t until penicillin became widely available in the 1940s that syphilis finally had a true cure.
Syphilis and Medical Ethics
The availability of penicillin makes one chapter of syphilis history particularly disturbing. Between 1932 and 1972, the U.S. Public Health Service ran a study on untreated syphilis in Tuskegee, Alabama. Researchers enrolled Black men with the disease but never obtained informed consent and never offered treatment, even after penicillin became standard care. The study continued for 40 years before news coverage forced it to end. In 1997, President Clinton issued a formal apology. The Tuskegee study led to sweeping reforms in research ethics and remains a lasting source of medical distrust in Black communities.
Syphilis Today
Despite being both preventable and curable with a simple course of antibiotics, syphilis is surging worldwide. New cases among adults aged 15 to 49 reached 8 million in 2022, an increase of over 1 million from previous estimates. The sharpest rises occurred in the Americas and Africa. Maternal syphilis, which can cause miscarriage, stillbirth, and severe birth defects, also spiked during the COVID-19 pandemic, with 1.1 million cases reported. The WHO’s goal of reducing annual syphilis infections from 7.1 million to 0.71 million by 2030 is moving in the wrong direction.
The disease that once devastated Renaissance Europe under a dozen different blame-laden names remains a major global health problem. The bacterium hasn’t changed much. What has changed is that treatment now exists, and the old mystery of “the French disease” is fully understood. The challenge is reaching the people who need that treatment before the infection progresses through its silent stages.