Syphilis cases are soaring—a doctor explains infection routes, symptoms, and prevention with doxyPEP

「昔の病気」と思われがちな梅毒は、いま20代を中心に報告が増えています。痛みのない初期症状に気づかないまま広がることも。自分とパートナーを守るための予防の選択肢を知っておきましょう。

梅毒はなぜ増えている？感染経路・症状・予防法とドキシPEP
Syphilis on the Rise: What You Need to Know NowInfection routes, symptoms, testing, and prevention with DoxyPEP explained

"Isn't syphilis a disease of the past?" — Many of you might have thought so. However, the number of syphilis patients in Japan continues to rise to record-high levels, spreading across all age groups, genders, and sexual orientations.

Syphilis is often hard to detect due to mild initial symptoms. If left untreated, it can cause severe damage to the heart, brain, and nerves years later. Furthermore, if a pregnant woman is infected, it can affect the baby as congenital syphilis.

In this article, a doctor from Mona Aoyama Clinic explains the current situation of syphilis, its infection routes, symptoms, testing, treatment, and prevention with DoxyPEP.

  • Syphilis testing and DoxyPEP prescriptions are available online.
  • At-home testing available with mail-in kits.
  • Same-day prescription and shipping (for payments made by 4 PM)

Syphilis Infection Status in Japan: Why Is It Increasing Now?

According to data from the National Institute of Infectious Diseases, the number of syphilis patients in Japan has been rapidly increasing since the 2010s, with over 10,000 cases reported annually in 2023. While infections among men who have sex with men (MSM) were once predominant, heterosexual infections and infections among women are now also increasing.

Item Content
Increasing Trend Rapid increase since the 2010s. Over 10,000 cases reported annually in 2023 (record-high levels).
Shift in Infected Population Previously MSM, now rapidly increasing in heterosexual and female populations.
Age Group Mainly 20s to 40s. A notable increase in young women.
Congenital Syphilis Reports of congenital syphilis in infants are increasing due to the rise in infections among pregnant women.

Syphilis Transmission Routes

  • Sexual intercourse (most common): Can be transmitted through vaginal sex, anal sex, and oral sex.
  • Contact with mucous membranes or open wounds: Direct contact with syphilis lesions (ulcers, rashes).
  • Mother-to-child transmission (congenital syphilis): Transmitted from an infected mother to the fetus via the placenta.
  • Blood transmission: Sharing needles, etc. (rare).

💡 Condoms offer some protection against syphilis, but they are not 100% effective as infection can occur through contact with lesions in areas not covered (e.g., genitals, around the mouth).

Can Syphilis Be Transmitted Through Kissing?

Syphilis can be transmitted through kissing, not just sexual intercourse. Lesions (chancres or rashes) that appear in the mouth or on the lips during primary or secondary syphilis can cause infection through mucous membranes upon contact. It's important to note that you cannot assume you are safe just because you haven't engaged in sexual activity. If your partner has any concerning symptoms around their mouth, it is advisable to be cautious, even with kissing.

Syphilis Symptoms: By Stage

Stage Timing Main Symptoms Characteristics
Primary 3-6 weeks after infection Hard chancre (painless sore) appears at the site of infection (genitals, mouth, anus, etc.) Painless and disappears naturally, making it easy to overlook.
Secondary 3-12 weeks after infection Generalized rash (including palms and soles), fever, swollen lymph nodes, oral sores. Symptoms are diverse and can be mistaken for other conditions. This is the most infectious stage.
Latent After secondary stage, for several years No symptoms Infection goes unnoticed without testing. Risk of transmission to others.
Tertiary/Late Several years later Severe damage to the heart, aorta, brain, and nerves (neurosyphilis, cardiovascular syphilis). Can become life-threatening if left untreated.

⚠️ "Symptoms disappearing" does not mean "cured." Syphilis symptoms may resolve naturally, but the bacteria remain in the body. The infection remains contagious even after symptoms disappear, and if left untreated, it will become severe. Always get tested and treated.

If You Have These Symptoms, Get Tested Immediately

  • You have developed a painless sore on your genitals, mouth, or anus.
  • You have a rash all over your body, including your palms and soles.
  • You have persistent unexplained fever or swollen lymph nodes.
  • Your partner has been diagnosed with syphilis.
  • You have had sexual contact with multiple partners and have concerns.

Symptoms may disappear naturally, but this does not mean you are cured; it means the infection is progressing internally. If you have any concerns, get tested regardless of symptoms.

Syphilis Testing and Treatment

Syphilis treatment varies by stage and may involve oral medication or injections. The standard treatment recommended by national and international guidelines is intramuscular injection of benzathine penicillin G, a long-acting penicillin formulation. For primary and secondary syphilis, one injection is often sufficient for a cure. If penicillin allergy or other contraindications prevent injection, alternative treatments such as oral doxycycline may be considered.

Injection treatment requires an in-person visit to a medical facility. Our clinic offers online consultations and testing guidance. If injection treatment is necessary, we will guide you to an in-person visit.

Item Content
Testing Method Blood test (Treponema pallidum antibody, RPR). Detectable 3-4 weeks after sexual contact.
Treatment Method Oral penicillin-based antibiotics (e.g., amoxicillin). Curable in stages 1-2.
Treatment Period Stages 1-2: Approximately 2-4 weeks. Late-stage requires longer treatment.
Our Clinic's Services Online consultation, mail-in test kit, and prescription services available.

For Pregnant Individuals

If a pregnant woman contracts syphilis, it can be transmitted to the fetus via the placenta, leading to congenital syphilis (miscarriage, stillbirth, or disabilities after birth). While syphilis testing is performed during prenatal check-ups in Japan, infection can occur between check-ups. If your partner is diagnosed with syphilis, or if you have had sexual contact that raises concerns, get tested without waiting for your next check-up. Treatment during pregnancy requires consideration of the fetus's health, so an in-person examination is always necessary.

Regarding Your Partner

Syphilis is highly contagious and carries a high risk of transmission to partners. If you test positive, encourage your partner to get tested, regardless of whether they have symptoms. If you find it difficult to tell them, please consult our clinic; we can advise you on how to approach the situation.

Syphilis Prevention with DoxyPEP

Clinical trials have shown that taking DoxyPEP within 72 hours after condomless sex can prevent syphilis infection by approximately 70-80%. It is the most established STD prophylactic for syphilis prevention.

  • Timing: Once within 72 hours (3 days) after sexual activity.
  • Dosage: Doxycycline 200mg (100mg x 2 tablets).
  • Target: Especially MSM (men who have sex with men) and transgender women. However, anyone who has engaged in risky sexual activity should consult a doctor.
  • Prevention effectiveness is maximized when combined with regular testing.

Frequently Asked Questions

I have a rash on my palms. Could it be syphilis?
Rashes on the palms and soles are typical symptoms of secondary syphilis. If you have any concerns, get tested immediately. Syphilis rashes often do not itch and can be difficult to distinguish from drug rashes or allergies.
Once syphilis is cured, do I become immune?
No, you do not. Even if syphilis is completely cured with treatment, immunity does not remain, so you can be reinfected. Regular testing and prevention (using DoxyPEP, condoms) are necessary even after recovery.
Can I still get syphilis even if I take DoxyPEP?

With a prevention rate of approximately 70-80%, there is a 20-30% chance that infection can still occur. It is important to undergo regular syphilis testing and seek early treatment if infected.

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