Syphilis is a bacterial infection caused by the organism Treponema pallidum. This infection is highly responsive to treatment with the antibiotic Penicillin G, which is the preferred and most effective treatment for all stages of the disease, including during pregnancy. While a single injection is often associated with cure, the process of the infection “going away” involves a sequence of physical changes and a long-term medical monitoring process. The time it takes for a person to be considered cured depends on the stage of the infection and the medical definition of “gone.”
Stage-Specific Treatment Requirements
The regimen for administering Penicillin G depends on how long the Treponema pallidum bacteria has been present in the body. Benzathine Penicillin G is used to maintain a therapeutic level of the antibiotic in the bloodstream for a sustained period, effectively targeting the slow-dividing bacteria.
For individuals diagnosed with early-stage syphilis (primary, secondary, and early latent infections acquired within the last year), a single intramuscular injection of 2.4 million units of Benzathine Penicillin G is the standard treatment. This single dose is sufficient because the bacterial load is generally lower and more accessible to the antibiotic.
In contrast, treatment for late latent syphilis (infection lasting longer than one year or of unknown duration) requires a multi-dose approach. The protocol involves a total of 7.2 million units of Benzathine Penicillin G, delivered as three separate injections of 2.4 million units each. These injections are typically administered at one-week intervals to ensure the sustained presence of the drug necessary to eliminate the bacteria.
Immediate Post-Injection Reactions and Symptom Resolution
Shortly after receiving the penicillin injection, some patients experience an acute, temporary reaction known as the Jarisch-Herxheimer Reaction (JHR). This common phenomenon is a sign that the treatment is actively working and is caused by the rapid release of toxins as large numbers of bacteria are killed off.
Symptoms of the JHR are flu-like, including fever, chills, headache, and muscle aches, often peaking 4 to 12 hours after the shot. The reaction is usually self-limiting and resolves spontaneously within 12 to 24 hours without causing long-term problems.
The physical symptoms of syphilis begin to resolve over days to weeks following treatment. The painless sore of primary syphilis (chancre) typically heals within one to three weeks. For secondary syphilis, the widespread rash gradually fades over several weeks. However, the disappearance of these visible signs does not mean the infection is medically cured, as bacteria may still be present in the body.
Confirming Cure Through Follow-Up Testing
The definitive answer to how long it takes for syphilis to “go away” is determined by long-term serological monitoring. Medical cure is confirmed through a sustained drop in antibody levels in the blood over months, not at the time of injection. This monitoring is performed using non-treponemal tests, such as the RPR (Rapid Plasma Reagin) or VDRL (Venereal Disease Research Laboratory) tests.
These tests measure the level of antibodies in the blood, expressed as a titer. Successful treatment is defined by a significant, sustained four-fold decrease in this titer, which represents a drop by two dilutions. This reduction confirms that the body’s immune response is diminishing, indicating that the bacteria have been eliminated.
The timeline for achieving this serological cure varies depending on the stage of the initial infection. For primary or secondary syphilis, a four-fold decrease in the titer is typically expected within 6 to 12 months after treatment. Patients treated for latent syphilis, a later stage, may take longer, with the four-fold drop expected within 12 to 24 months.
Healthcare providers typically recommend a specific schedule for follow-up blood tests (e.g., 6, 12, and 24 months post-treatment) to track this titer decline. If the titers do not drop sufficiently or if they increase four-fold, it may suggest treatment failure or a new infection, requiring further medical evaluation. A small number of successfully treated individuals may have a persistently low, non-declining titer, a phenomenon called “serofast,” which usually does not require further treatment.