Reinfection and Relapse After Treatment of Early Syphilis With Penicillin

Mathematics of a sex‐structured model for syphilis transmission dynamics

“…It is worth emphasizing that, although the reinfection of recovered individuals is an important and well‐known feature of syphilis transmission dynamics, many of the published modeling studies in the literature do not incorporate such property (and, as a consequence, fail to capture the reinfection‐induced backward bifurcation property of the disease). This study is one of the very first to theoretically illustrate the phenomenon of backward bifurcation in syphilis transmission dynamics (Milner and Zhao also showed the presence of backward bifurcation in syphilis dynamics and used this property to explain the resurgence of syphilis in recent decades).…”

“…The proof of Theorem , based on using center manifold theory, is given in Appendix (the associated backward bifurcation diagram is depicted in Figure ). The epidemiological implication of Theorem is that the classical epidemiological requirement of having , while necessary, is no longer sufficient for the effective control of (or elimination of) the disease in the community.…”

“…Infected individuals who have syphilis longer than a year may require additional doses). Infected individuals who recovered from syphilis infection do not acquire permanent immunity against reinfection (hence, reinfection and relapse of infected individuals who have recovered from syphilis infection after treatment can occur at any stages of the infection.…”

Treatment of Early Venereal Syphilis with Antibiotics

“…Lesinska (1961) found that the reaction became negative within 6-18 months in about two-thirds of patients with early syphilis, more commonly in primary syphilis, but that constant positive results should not be regarded as due to treatment failure (see also Nielsen, 1961 It is frequently very difficult to distinguish relapse from re-infection (Schamberg and Steiger, 1948;Schamberg, 1950), and a patient rapidly cured of syphilis with penicillin can also rapidly be re-infected. Careful consideration of many of the so-called early relapses following penicillin therapy has indicated that many, indeed up to one-half and more of so-called failures, are in fact re-infections (Thomas and Landy, 1950;Schoch and Alexander, 1949;Rajam, Krishnamurthi, and Rangiah, 1955), many of which are of the "ping-pong" type between regular partners. If this is so, a lower re-treatment rate would be expected when the treatment time with penicillin is prolonged (such has been shown to be the case-see Table VI), and also when syphilis is less common and the patient is less able to become re-infected in spite of additional sexual adventures.…”

Treatment of Early Venereal Syphilis with Antibiotics

“…It is frequently very difficult to distinguish relapse from re-infection (Schamberg and Steiger, 1948;Schamberg, 1950), and a patient rapidly cured of syphilis with penicillin can also rapidly be re-infected. Careful consideration of many of the so-called early relapses following penicillin therapy has indicated that many, indeed up to one-half and more of so-called failures, are in fact re-infections (Thomas and Landy, 1950;Schoch and Alexander, 1949;Rajam, Krishnamurthi, and Rangiah, 1955), many of which are of the "ping-pong" type between regular partners. If this is so, a lower re-treatment rate would be expected when the treatment time with penicillin is prolonged (such has been shown to be the case-see Table VI), and also when syphilis is less common and the patient is less able to become re-infected in spite of additional sexual adventures.…”