Causes of syphilis: how it is transmitted and who is at risk

Syphilis is not caused by a weakened immune system, hypothermia, stress, or poor hygiene, but by infection with a specific bacterium—Treponema pallidum. This spiral-shaped microorganism can penetrate mucous membranes and microdamage to the skin, then spread throughout the body via the blood and lymphatic system. [1]

Treponema pallidum causes both acquired syphilis, transmitted primarily through sexual contact, and congenital syphilis, which occurs when the infection is transmitted from a pregnant woman to her fetus. Therefore, it is important to separate the term "cause" in medicine into two levels: the immediate cause—the bacteria—and the route of infection—the way it enters the body. [2]

Once the bacteria has entered, the first signs often don't appear immediately. The incubation period is usually about 21 days, but can range from 9 to 90 days, so a person may not associate the ulcer with a specific sexual encounter. [3]

Treponema pallidum does not remain confined to the skin's surface. Even in its early stages, it can spread through the blood and lymphatic system, which explains the subsequent development of a rash, lesions of the mucous membranes, lymph nodes, and, if left untreated, complications affecting the nervous system, eyes, hearing, heart, and other organs. [4]

Syphilis is a curable infection, but recovery does not provide lifelong immunity. After successful treatment, a person can become infected again if they have further contact with an infected partner. [5]

Reason level	What does this mean?	Practical significance
Immediate cause	Treponema pallidum	Without this bacterium, syphilis does not occur
Sexual tract	Contact with a contagious ulcer or mucous lesion	The main route of acquired syphilis
Vertical path	Transmission from pregnant woman to fetus	Cause of congenital syphilis
Reinfection	New contact after treatment	Immunity after illness does not provide reliable protection
Social factors	Late testing, untreated partners, barriers to care	Support the spread of infection
Mythical reasons	Stress, cold, household dirt	Do not cause syphilis without bacteria

The table shows that the real cause of syphilis is always associated with the pale treponema, and not with the household circumstances themselves. [6]

Why does infection most often occur through sexual contact?

The primary mechanism of infection is direct contact of the skin or mucous membrane with a syphilitic lesion. Such a lesion may be a primary chancre, a mucous plaque, a broad condyloma, or another element of early syphilis containing Treponema pallidum. [7]

Infection is possible through vaginal, anal, and oral sex. The bacteria can enter the body through the mucous membranes of the genitals, rectum, lips, tongue, throat, or through microscopic breaks in the skin, which a person usually does not notice. [8]

Ejaculation is not a necessary condition for transmission. Syphilis infection is transmitted not only through genital secretions, but primarily through direct contact with an infectious ulcer or moist mucous lesion. [9]

Early forms of syphilis, when there are visible or hidden mucocutaneous lesions, are generally considered the most contagious. Late latent infection without superficial lesions is significantly less associated with sexual transmission, but during pregnancy, even asymptomatic infection can pose a risk to the fetus. [10]

Condoms reduce the risk, but do not eliminate it completely. If the infection is located in an area not covered by a condom, such as the scrotum, pubic area, external vulva, perineum, around the anus, or on the labium, contact with it can still result in infection. [11]

Contact type	Could it be the cause of infection?	Why
Vaginal sex	Yes	Contact of mucous membranes with a chancre or mucous plaque is possible.
Anal sex	Yes	The rectum and anal area can be portals of entry
Oral sex	Yes	Lesions may be in the mouth or on the genitals
Skin contact with the ulcer	Yes	The bacterium is in an infectious lesion
Sexual intercourse without ejaculation	Yes	Transmission is possible through contact with the lesion.
Sex with a condom	The risk is lower, but not zero.	The condom does not cover all areas of skin
No visible ulcers	Does not guarantee safety	The lesion may be hidden

The practical conclusion is that syphilis is not transmitted “through the fact of sex itself,” but through contact with an infectious lesion, which is often painless and unnoticeable. [12]

Why chancre and early symptoms often go unnoticed

One of the reasons syphilis spreads is its latent or subtle onset. The primary chancre is often painless, non-itchy, and can heal on its own within a few weeks, so a person may not seek medical attention and may continue to have sex. [13]

In women, chancres can be located in the vagina or on the cervix; in men, under the foreskin or inside the urethra; in people of either sex, in the rectum, on the tonsil, tongue, or inner surface of the lip. Such locations cannot be reliably detected during a routine self-examination. [14]

The secondary stage is also not always recognized. The rash may be pale, non-itchy, appear on the palms and soles, or resemble a drug reaction, viral infection, fungal infection, psoriasis, or another skin condition. [15]

When a sore or rash disappears without treatment, it creates a false sense of recovery. In reality, the infection may enter a latent stage, in which a person has no visible symptoms, but laboratory tests remain positive. [16]

Early tests also don't always immediately detect infection. Early in primary syphilis, antibodies may be too low to detect, so a negative test soon after exposure doesn't always definitively rule out infection. [17]

Why is syphilis missed?	What's happening
The chancre doesn't hurt.	The person does not consider the ulcer to be dangerous
The lesion is hidden inside the body	It is impossible to see it on your own.
The rash resembles other diseases	The patient is treating "allergy" or "dermatitis"
The symptoms go away on their own.	An illusion of recovery arises
The test was taken too early	Antibodies may not yet be detected
The partner looks healthy	The infection may be asymptomatic or latent.

It is this latent course that makes syphilis a disease in which preventative testing and partner screening are as important as recognizing the symptoms. [18]

Transmission through oral sex and mouth lesions

Oral sex is a real route of syphilis transmission. If the lips, tongue, oral mucosa, or pharynx come into contact with a partner's infected lesion, Treponema pallidum can penetrate the mucosa and cause a primary chancre in the mouth or lip. [19]

The opposite situation is also possible: if a person has a syphilitic lesion on the lip, tongue, tonsil, or oral mucosa, they can transmit the infection to a partner through oral contact. Therefore, syphilis is not limited to the genital area. [20]

Kissing is not considered a common household route of transmission, but direct contact with an active syphilitic ulcer or mucous plaque in the mouth is potentially dangerous. The risk is not associated with regular saliva, but with the presence of an infectious lesion on the contacting surface. [21]

The risk of oral contact may increase with bleeding gums, stomatitis, cracked lips, recent piercings, mucosal injuries, or sore throat. Even without a visible wound, the mucosa can be an entry point for the pathogen through direct contact with the chancre. [22]

Oral syphilitic lesions are often mistaken for herpes, aphthae, trauma, sore throat, or inflammation following a dental procedure. Therefore, a persistent ulcer on the lip, tongue, tonsil, or oral mucosa following sexual contact requires not only local treatment but also testing for syphilis. [23]

Situation	Could it be the cause of infection?	Comment
Oral contact with genital chancre	Yes	Possible chancre in the mouth or lip
Oral contact with anal lesion	Yes	The risk is associated with direct contact with the mucous membrane.
Syphilitic ulcer in the partner's mouth	Yes	The infection can be transmitted through oral sex.
Kissing for a lip ulcer	Potentially yes	The risk is associated with active damage
A normal kiss without defeats	Not a typical path	An infectious element is needed
Common cup	Not considered a transmission route	The bacteria does not survive well outside the body.

The main practical conclusion: oral sex reduces the risk of some infections compared with other practices, but does not exclude syphilis. [24]

Transmission from pregnant woman to fetus

Congenital syphilis occurs when Treponema pallidum is transmitted from a pregnant woman to her fetus through the placenta. This is not a household infection of the child after birth, but an intrauterine infection associated with untreated, late-diagnosed, or inadequately treated syphilis in the mother. [25]

The risk of transmission is especially high with early syphilis in pregnant women, because the body typically has more active bacteria. However, latent infection can also be dangerous, even if the woman has no ulcers, rash, or other symptoms. [26]

Untreated syphilis during pregnancy can lead to miscarriage, stillbirth, preterm birth, low birth weight, neonatal death, and congenital syphilis. The World Health Organization considers the detection and treatment of syphilis in pregnant women a key measure to prevent severe outcomes. [27]

Congenital syphilis is often caused not only by the infection itself, but also by missed opportunities for prevention: lack of timely prenatal care, late testing, lack of treatment, incomplete treatment, or reinfection from an untreated partner. [28]

In 2024, the European Centre for Disease Prevention and Control reported that the number of reported cases of congenital syphilis in the European Union and European Economic Area was the highest since coordinated surveillance began in 2009 and had almost doubled compared to 2023. [29]

Cause of congenital syphilis	How does it work?
Untreated syphilis in a pregnant woman	Bacteria cross the placenta
Late detection	Treatment begins too close to birth
Incomplete treatment	The mother's infection may persist.
Reinfection	An untreated partner infects a woman again
Lack of prenatal care	The analysis is not completed on time
Insufficient testing during pregnancy	A new infection after an early negative test goes undetected
Lack of treatment for partner	The retransmission source is preserved

Congenital syphilis is preventable in many cases if the pregnant woman is tested promptly, receives proper treatment with penicillin, and the partner is also tested and treated. [30]

Behavioral and sexual risk factors

Risk factors do not independently cause syphilis without Treponema pallidum, but they do increase the likelihood of encountering an infectious partner or an undetected infectious lesion. Therefore, in clinical practice, risk is assessed not as a person's moral characteristic, but as the medical probability of exposure to the pathogen. [31]

Risk factors include a new partner, multiple partners, anonymous contacts, a partner with a sexually transmitted infection, inconsistent condom use, commercial sex, and substance use in sexual situations.[32]

Men who have sex with men remain a disproportionately affected group in many countries, with syphilis rates not related to sexual orientation as a biological cause, but to the network structure of contacts, frequency of testing, number of partners, and local outbreaks. [33]

In Europe, data from 2024 show that among cases with a known transmission category, the majority were reported among men who have sex with men, but since 2021, a steady increase has also been observed among heterosexual men and women. This is important because syphilis cannot be considered a problem of only one group. [34]

Having another sexually transmitted infection increases the likelihood of being diagnosed with syphilis not only because of the shared routes of transmission, but also because ulcers, inflammation, and frequent contact with high-risk sexual partners increase the chance of new infection.[35]

Risk factor	Why is the risk higher?
New partner	The current status of infections is unknown.
Several partners	More likely to come into contact with an infectious person
Anonymous contacts	It is more difficult to notify the partner and pass the control
Irregular use of condoms	More direct contact between skin and mucous membranes
Partner with syphilis	Direct confirmation of risk
Recent other sexually transmitted infection	Common transmission routes and risky sexual networks
Commercial sexual contacts	Often the frequency of partner changes is higher
Sex in the context of psychoactive substances	Control over protection and agreed boundaries may be reduced.

Risk assessment is not needed for stigmatization, but to determine the frequency of testing, the need for partner testing, and timely preventive treatment after confirmed contact. [36]

Why can you get syphilis again?

Successful treatment eradicates the current infection but does not render a person immune to Treponema pallidum. If, after treatment, a partner is exposed to the infectious lesion again, reinfection and a new episode of syphilis are possible. [37]

Reinfection is often confused with a "relapse" of an old infection. In reality, after adequate therapy and proper titer reduction, a new rise in titers usually prompts the physician to evaluate recent contacts and the likelihood of new transmission. [38]

The risk of reinfection is particularly high if only one partner is treated. An untreated regular partner can transmit the infection again after completing therapy, so notification, testing, and treatment of partners are part of eliminating the cause of further transmission. [39]

A positive treponemal test after treatment does not prove reinfection, because such antibodies persist for a long time or even for life in most people. Symptoms, contacts, and changes in quantitative non-treponemal titers are important for identifying new infection. [40]

The absence of symptoms in a partner also does not rule out their contagiousness. The primary chancre may be latent, secondary lesions may be unnoticeable, and an early test may still be negative if contact occurred recently. [41]

Scenario	What's happening
The man was successfully treated	The old infection has been destroyed.
The partner was not treated	Retransmission is possible
A new partner has appeared	A new risk is emerging
The treponemal test remained positive.	This could be a trace of past syphilis.
Non-treponemal titer increased 4-fold	New infection or treatment failure is possible
The symptoms have returned.	A new examination and tests are needed.
The partner has no complaints	Latent syphilis is still possible

The main cause of recurrent syphilis is not "weak treatment" but new contact with Treponema pallidum, especially if partners are not examined and treated at the same time. [42]

The role of diagnosis and access to medicine in the spread of syphilis

Syphilis spreads more easily where people seek medical care late, are not routinely tested, or do not receive treatment immediately after a positive result. Because the infection often has no noticeable symptoms, the lack of accessible diagnostics directly supports hidden transmission. [43]

Laboratory diagnosis of syphilis requires the correct combination of treponemal and nontreponemal tests. Misinterpretation of a single isolated test can lead to both missing an active infection and unnecessary treatment of a person with previously cured syphilis. [44]

Delays in partner treatment also support transmission. If one person is infected but their recent partners are not notified, tested, or given preventive treatment when indicated, the chain of infection continues. [45]

For congenital syphilis, the role of access to care is particularly evident. An analysis of data from the US Centers for Disease Control and Prevention found that lack of timely testing and adequate treatment during pregnancy contributed to the majority of congenital syphilis cases in 2022. [46]

Social barriers—stigma, fear of disclosure, lack of access to clinics, lack of insurance, unstable housing, substance use, migration and language barriers—are not a biological cause of syphilis, but may prevent timely testing and treatment. [47]

Systemic factor	How it increases spread
Unavailability of testing	Asymptomatic cases are not detected
Late treatment	The infection remains contagious longer
Untreated partners	Repeated transmissions occur
Misinterpretation of tests	An active case may be missed
Stigma	People are putting off conversion
Lack of prenatal care	The risk of congenital syphilis is increasing
Loss of contact with the patient	Difficulty completing treatment and follow-up
Language and migration barriers	Access to prevention is declining

At the public health level, the reasons for the rise in syphilis often lie not only in individual behavior, but also in the availability of testing, partner services, treatment, and antenatal care. [48]

Causes of infection in newborns and children

In newborns, syphilis is usually caused by intrauterine transmission from the mother, rather than exposure to the external environment after birth. Treponema pallidum can cross the placenta and infect the fetus even before birth. [49]

Congenital syphilis can develop if the infection was not detected in a pregnant woman, treatment was started too late, was incomplete, or the woman was reinfected after an earlier negative test. Therefore, prevention in the child begins with examination and treatment of the mother. [50]

Many infected children show no obvious signs immediately after birth. This means that the cause of the disease may be missed if the newborn's appearance is used alone and the mother's tests, treatment timing, and serological titers are not taken into account. [51]

Early congenital syphilis may present with a runny nose, rash, enlarged liver and spleen, jaundice, anemia, decreased platelet count, and bone damage. Later manifestations may affect teeth, bones, vision, hearing, and the nervous system. [52]

Household transmission of syphilis to children through dishes, towels, or swimming pools is not considered a typical mechanism. If acquired syphilis is suspected in a child, physicians are required to assess the medical, social, and protective aspects of the situation, as sexual transmission in children requires special investigation and protection. [53]

The child's situation	The most likely reason
Positive signs immediately after birth	Intrauterine transmission
The mother was not examined during pregnancy	Missed maternal syphilis
The mother was treated too late.	Insufficient time to protect the fetus
The mother's partner was not treated	Reinfection of a woman
The baby appears healthy at birth	Congenital infection is still possible
Late hearing or dental problems	Possible late manifestation of congenital syphilis
Suspected acquired syphilis in a child	Urgent medical and protective assessment required

Congenital syphilis is largely preventable because prompt testing and treatment of the pregnant woman with penicillin significantly reduces the risk of transmission to the fetus.[54]

What does not cause syphilis?

Syphilis does not occur as a result of hypothermia, weakened immunity, stress, poor nutrition, masturbation, swimming, or using a public restroom. These conditions may affect overall health or behavior, but they do not, by themselves, cause infection without the presence of Treponema pallidum. [55]

Syphilis is not spread through toilet seats, door handles, bathtubs, swimming pools, clothing, hugs, or shared living spaces. Typical transmission requires direct contact with an infectious lesion or transmission from a pregnant woman to her fetus. [56]

Common dishes, cups, or cutlery are not considered a cause of infection. Theoretical fears surrounding "saliva on a mug" do not correspond to the basic biological mechanism of syphilis: the bacteria survive poorly outside the body and are transmitted through an active lesion. [57]

The human immunodeficiency virus does not cause syphilis. However, ulcerative infections, including syphilis, may increase the likelihood of HIV transmission, and the combination of infections requires closer monitoring and testing. [58]

Contraceptive pills, intrauterine devices, and hormonal medications do not cause syphilis and do not protect against it. They can prevent pregnancy, but they do not create a barrier between mucous membranes and infectious lesions. [59]

Myth	Reality
"You can get infected through the toilet."	This is not a typical route of transmission of syphilis.
"Syphilis is caused by dirt."	Treponema pallidum is needed.
"Stress causes syphilis"	Stress does not create bacteria
"Hypothermia triggers syphilis"	Syphilis does not occur without infection.
"Dishes are dangerous"	Transmission through utensils is not considered a route
"The human immunodeficiency virus causes syphilis."	These are different infections.
"Contraceptives protect against syphilis"	They are not a barrier to bacteria.
"If there is no ulcer, there is no risk."	The lesion may be hidden

Distinguishing between real causes and myths helps avoid unnecessary fear of everyday situations and at the same time not to underestimate real sexual and perinatal risks. [60]

Why syphilis rates are rising in some countries

The rise in syphilis in the population is usually not explained by a single cause. It is influenced by sexual networks, frequency of partner change, use of barrier protection, availability of testing, speed of treatment, effectiveness of partner services, and social barriers to medical care. [61]

In the European Union and the European Economic Area, there were 45,577 confirmed cases of syphilis reported in 29 countries in 2024, with an incidence rate of 10.8 cases per 100,000 population in countries with comprehensive surveillance. These data indicate that syphilis remains a current infection rather than a historical disease. [62]

European data from 2024 show higher rates among men, particularly those aged 25–34, and a significant proportion of cases among men who have sex with men. At the same time, an increase among heterosexual men and women since 2021 indicates broader transmission outside key groups. [63]

In the United States, preliminary data for 2024 showed a continued high burden of sexually transmitted infections and a further increase in congenital syphilis for the 12th consecutive year. This highlights the role of missed testing, late treatment, and inadequate prenatal care coverage among pregnant women. [64]

Part of the increase in registered cases may also reflect improved detection, especially in groups that are regularly tested. But even with the impact of more active screening, the rise in congenital syphilis points to real failures in prevention, because each such case is associated with an infection in a pregnant woman that should have been detected and treated promptly. [65]

Population cause	How does it affect the growth of cases?
Asymptomatic course	People are unaware of the infection.
Insufficient testing	The infection remains latent longer
Untreated partners	The transmission continues in the network of contacts
Reducing the use of barriers	Direct contact of mucous membranes occurs more often
Large sexual networks	The infection spreads faster
Late antenatal care	The risk of congenital syphilis is increasing
Stigma and fear	People are putting off conversion
Improving detection	Part of the increase in statistics is due to the increased number of tests.

Modern epidemiology of syphilis shows that the causes of spread are simultaneously at the individual, partner, medical and societal levels. [66]

How Understanding the Causes Helps Prevent Syphilis

If the primary cause of syphilis is exposure to Treponema pallidum through contact with an infectious lesion, prevention should reduce the likelihood of such exposure. Therefore, condoms, barrier napkins for oral sex, avoiding contact with sores, and regular testing for new or multiple partners are important. [67]

Because lesions are often hidden, prevention cannot rely solely on a physical examination of the partner. It is more reliable to discuss testing, use barrier methods, and undergo testing at the recommended times, especially when interacting with new or multiple partners. [68]

After confirmed contact with a person with early syphilis, medical management may include prophylactic treatment even if the early test is negative. This is because the infection may be in the incubation period or diagnostic window. [69]

During pregnancy, understanding the causes is especially important: the absence of symptoms in the mother does not rule out transmission to the fetus. Therefore, prevention of congenital syphilis is based on early testing, repeat testing if there is a risk, timely treatment with penicillin, and partner testing. [70]

At the community level, the most effective interventions are accessible sexual health clinics, rapid testing, confidential partner services, antenatal care, stigma-free education programs, and timely treatment. These interventions do not directly target the bacteria, but rather address the conditions that allow it to be transmitted from person to person. [71]

Cause or factor	Preventive response
Contact with a contagious ulcer	Barrier protection and avoidance of contact in case of injuries
Hidden chancre	Regular testing
New or multiple partners	Discussion of tests and condoms
Confirmed syphilis in a partner	Urgent medical assessment
Incubation period	Repeated tests and treatment as indicated
Pregnancy	Early and repeat screening
Untreated partner	Notification and treatment of partners
Stigma and lack of access to help	Confidential and accessible services

Understanding the causes of syphilis helps to avoid blaming the person, but to quickly break the chain of transmission: identify the infection, treat the patient, examine partners and prevent new cases. [72]

Key points from experts

Margaret Kingston, Consultant Genitourinary Physician at Manchester University NHS Foundation Trust and lead author of the 2024 UK Syphilis Guidelines, emphasises that transmission is by direct contact with an infectious lesion or from mother to fetus, and that early dissemination of the bacterium through the blood and lymphatic system explains the wide range of presentations.[73]

John R. Papp, PhD, a specialist in the Division of Sexually Transmitted Infection Prevention at the U.S. Centers for Disease Control and Prevention, is the lead author of the 2024 syphilis laboratory guidelines. His working group's key practical finding: occult infection and early false-negative results make laboratory testing a critical tool for breaking the chain of transmission. [74]

Kimberly Workowski, MD, professor of infectious diseases at Emory University School of Medicine and lead author of the U.S. guidelines on sexually transmitted infections, emphasizes that the causes of new infections cannot be addressed by treating the patient alone; partners must also be identified, the risk of recent exposure assessed, and preventive treatment administered as indicated. [75]

Edward Hook III, MD, professor of infectious diseases and epidemiology at the University of Alabama at Birmingham, is an expert in the prevention, diagnosis, and treatment of syphilis. His area of expertise includes how sexually transmitted infections are spread and how to prevent them; this directly relates to understanding syphilis as a disease of sexual networks, not just individual contact. [76]

Laura Hinkle Bachmann, MD, MPH, is the chief medical officer for the Division of Sexually Transmitted Infection Prevention at the U.S. Centers for Disease Control and Prevention. Her work on recommendations for post-exposure prophylaxis with doxycycline reflects the current approach: the causes of syphilis require a combination of testing, treatment, post-exposure prophylaxis, and regular surveillance in high-risk groups. [77]

Frequently asked questions

What is the main cause of syphilis? The main cause is infection with the bacterium Treponema pallidum. Without this pathogen entering the body, syphilis does not occur. [78]

Does syphilis result from poor hygiene? No. Poor hygiene can worsen skin or mucous membrane conditions, but syphilis only occurs when infected with Treponema pallidum. [79]

Can you become infected with syphilis through non-ejaculatory sex? Yes. Transmission is through contact with an infectious ulcer or mucous lesion, so ejaculation is not required. [80]

Can you become infected through oral sex? Yes. Treponema pallidum can be transmitted through contact between the oral mucosa and a lesion on the genitals, anal area, or in the mouth of a partner. [81]

Can you become infected through kissing? A simple kiss without active lesions is not considered a typical route of transmission, but direct contact with a syphilitic ulcer or plaque on the lip or mouth can be dangerous. [82]

Can you become infected through a toilet? No. Transmission via a toilet seat is not considered a route of spread of syphilis. [83]

Can you get infected through a pool or bathtub? No. Syphilis is not spread through pools, bathtubs, or water during normal household contact. [84]

Can you become infected by sharing a teacup? This is not considered a typical route of transmission because syphilis requires direct contact with an infectious lesion. [85]

Why doesn't a condom provide 100% protection? It only covers part of the skin and mucous membranes. If the ulcer is located outside the covered area, contact with it can lead to infection. [86]

Can a partner be contagious without symptoms? Yes. Lesions may be hidden, painless, or unnoticed, and latent infection is only detectable in a laboratory. [87]

Why is a chancre often overlooked? It is often painless, can be small, and located inside the vagina, rectum, mouth, or under the foreskin. [88]

Can stress cause syphilis? No. Stress does not create Treponema pallidum and is not a cause of syphilis. [89]

Can a weakened immune system cause syphilis? A weakened immune system does not cause syphilis per se, but it can alter the course of the infection after infection. Treponema pallidum remains the direct cause. [90]

Is it possible to become reinfected after treatment? Yes. Reliable immunity does not develop after treatment, so reinfection is possible with new contact with an infected partner. [91]

Why should a partner be treated? If a partner remains infected, they may be able to transmit Treponema pallidum again after the patient has completed treatment.[92]

Why is syphilis dangerous during pregnancy? Treponema pallidum can cross the placenta and infect the fetus, leading to congenital syphilis, stillbirth, premature birth, and other serious outcomes. [93]

Can a child be born with syphilis if the mother has no symptoms? Yes. Latent infection in a pregnant woman can proceed without complaints but remain dangerous to the fetus. [94]

Does the human immunodeficiency virus cause syphilis? No. They are different infections, but syphilitic sores may increase the risk of transmitting the human immunodeficiency virus through sexual contact. [95]

Why is syphilis increasing in some countries? Reasons include latent transmission, inadequate testing, untreated partners, large sexual networks, decreased barrier protection, and barriers to health care. [96]

Can a blood test determine the cause of infection? The test confirms the infection and helps assess the stage, but it usually cannot pinpoint the source of the infection. [97]

If the test is negative after contact, is there any cause for concern? A negative test too early does not always rule out infection, because antibodies may not yet be detectable. [98]

Can an antibiotic accidentally prevent syphilis? Sometimes an antibiotic can partially suppress the infection, but an accidental or incomplete course cannot be considered reliable prevention or treatment. [99]

Is there a vaccine that eliminates the cause of syphilis? No. As of 2026, there is no licensed vaccine against syphilis, and candidates are in preclinical development. [100]

What's the most important thing to do after exposure to someone with syphilis? It's important to seek immediate medical evaluation, get tested, and discuss preventative treatment, especially if the exposure occurred within the last 90 days. [101]

Conclusion

Syphilis is always caused by infection with the bacterium Treponema pallidum. Sexual contact, oral sex, hidden sores, untreated partners, and late testing do not cause the disease in themselves, but are conditions through which the bacteria are transmitted from person to person. [102]

Congenital syphilis has a different direct transmission pattern: the child is infected from the pregnant woman through the placenta. Therefore, prevention of this condition in newborns is based on early examination of the pregnant woman, treatment with penicillin, and prevention of reinfection. [103]

Understanding the causes helps us act without panic and myths: don’t be afraid of toilets, swimming pools and dishes, but take sexual contact, ulcers, rashes, regular testing, partner treatment and post-therapy monitoring seriously. [104]