The Topic of This Month Vol. 29, No. 9 (No. 343)

Sexually transmitted diseases in Japan as of 2007
(IASR 29: 239-241, September 2008)

In Japan, the sexually transmitted disease (STD) surveillance had been conducted under the Venereal Disease Prevention Law.  In addition, the five STDs were included in the target diseases of the National Epidemiological Surveillance of Infectious Diseases (NESID) from 1987 (IASR 19: 198-199, 1998).  After enactment of the Law Concerning the Prevention of Infectious Diseases and Medical Care for Patients of Infections (the Infectious Diseases Control Law) on April 1999, the physicians must notify syphilis cases to the near-by health center and STD sentinels report genital chlamydial infection, genital herpes, condyloma acuminatum and gonorrhea patients monthly under the NESID in accordance with the law (for reporting guidelines, refer to  Although sexual contact is also important in transmission of AIDS, amebiasis, hepatitis B and C, the trends of syphilis and four sentinel-reporting STDs since enactment of the Infectious Diseases Control Law are discussed in this topic.

Syphilis: The annual reports decreased until 2003, while changed to the increase in 2004, and particularly in 2006 and 2007, the respective increase was by 100 cases from the preceding year (see Table 1).  By the stage, early symptomatic cases (both primary and secondary) tended to increase since 2003 and asymptomatic cases since 2005 (Fig. 1).  The reports of asymptomatic cases prior to 2003 included such cases not agreeable to the reporting guidelines, whereas elderly cases decreased because the criteria of examination results for asymptomatic syphilis were applied strictly after April 2003 (see Fig. 2 and p. 246 of this issue).  Late symptomatic and congenital syphilis remained on the same level.  Child cases of congenital syphilis counted 10 in 2006, being the largest in number, whereas 7 cases were reported in 2008 (as of August 27) and further increase is anticipated (see p. 243 & 245 of this issue).

By stage, gender and age of 2,452 cases reported during 2004-2007, early symptomatic cases were seen from 15-19 years of males and prevalent among 20-44 years with a peak at 30-34 years, whereas of females, such were seen from as early as 10-14 years and prevalent among 15-39 years with a peak at 20-24 years (Fig. 2).  The ratio of primary to secondary cases was 1:1.1 among males and 1:1.9 among females; early symptomatic cases diagnosed in the secondary stage were more frequent among females. This is probably due to the fact that females may not be conscious of such symptoms at the primary stage as initial sclerosis and may consult a doctor for the first time with appearance of such symptoms at the secondary stage as macular syphilis.  Asymptomatic cases were reported among 15-94 years of both genders and the proportion of asymptomatic was 26% among males while as high as 46% among females, particularly high at 20-34 years (Fig. 2).  Asymptomatic syphilis was diagnosed by the tests done at the same time for diagnosis of other STDs, prior to blood donation, before entering a facility or pre-surgery.  Many asymptomatic cases are found among females probably because they have more opportunity of tests at medical checkup of the pregnant women and STD screening among commercial sex workers.

The infection routes of cases reported during 2004-2007 were sexual contact (excluding those given multiple routes) in 1,415 male cases (75% of them were heterosexual) and in 578 female cases (86% of them were heterosexual).  Other than sexual contact, infection routes of many cases were unknown, but mother-to-child infection was reported in 31 cases (2 of them had also heterosexual contact), blood transfusion in 8 cases, intravenous drug use in 4 casesi3 of them had also heterosexual contact), puncture in 4 cases (1 of them had also had also sexual contact), tattoo in 3 cases (2 of them had also sexual contact), and nursing care of patients in 1 case (who had also sexual contact).

Reports from the top 3 prefectures, Tokyo (452 cases), Aichi (207 cases) and Osaka (205 cases), accounted 35% of the total reports during 4 years, 2004-2007 (Table 1). On the other hand, incidence by prefecture during the 4 years (per 100,000 population as of October 1, 2007) was 8.21 in Kumamoto, 6.14 in Kochi, 5.96 in Kagawa, and 3.54 in Tokyo in the decreasing order.  In some prefectures, the total reports during the 4 years counted only a few.  It is necessary to make it known to physicians that syphilis is a mandatory reportable disease.

Sentinel reports of 4 STDs: For STD sentinels, approximately 970 medical institutions nationwide have been designated (as of June 2008, 466 obstetrics and gynecology, 397 urology, 93 dermatology, and 14 STD clinics).  Reports of cases per sentinel by gender (Fig. 4 and Table 2) show that cases of genital chlamydial infection and gonorrhea were on the continuous decrease in both genders from 2004 to 2007 and cases of genital herpes and condyloma acuminatum remained on approximately the same level.  In each year, the most prevalent in males were genital chlamydial infection (≈40% of the total cases of 4 STDs) followed by gonorrhea (≈30%), and in females, genital chlamydial infection (≈60%) followed by genital herpes (≈20%).

Three STDs other than genital herpes were prevalent among 20-34 years in males and rare in those ≥60 years, and in females, prevalent among 15-29 years and rare in those ≥55 years (Fig. 3).  On the other hand, the peak age group of genital herpes was older than those of other 3 STDs and many genital herpes cases were reported among older ages.  For the reason of this, recurrent cases, originally not the object of reporting, may have been reported.  To improve this problem, a sentence describing "to exclude obvious recurrent cases" was added in the reporting guidelines amended in April 2006.  No apparent change, however, has been recognized and it should be known to every sentinel clinic.

Concerning yearly change of each age group (Fig. 3), cases of genital chlamydial infection and gonorrhea have been on the decrease in almost all age groups, particularly in young age groups.  In contrast, cases of condyloma acuminatum have been on the increase in age groups older than 30s.

Current problems: In recent years, among Neisseria gonorrhoeae and Chlamydia trachomatis isolates, drug-resistant strains are on the increase (see p. 247 & 248 of this issue), and chlamydia with mutation on the PCR-targeted site of DNA, not detectable by PCR kits, have appeared (see p. 248 of this issue).

Although 5 STDs are not the targets of pathogen surveillance in NESID, Tokyo Metropolis originally collects specimens from 4 STD sentinels and conducts pathogen detections (see p. 252 of this issue).

In other countries, human papilloma virus (HPV) vaccine have been developed and introduced aiming at prevention of cervical cancer and condyloma acuminatum, although there are many unknown subjects to be solved (see p. 250 of this issue).

Because many superinfections occur in STDs (see p. 242 & 252 of this issue), it seems important at the time of the consultation to consider the possibility of other STDs connecting to early diagnosis and treatment.  It is also important to intervene in partners.

In all 5 STDs, cases of 10-14 years have been reported.  As asymptomatic cases of genital chlamydial infection have been reported in approximately 13% among female high school students (the study group of the Ministry of Health, Labour and Welfare), it is apparently important to start education on STD prevention for junior high school students.  Establishment of a system of consultation and testing, leading to action for taking appropriate medical advice at the time when young people notice their symptom appearance by themselves, is a matter of urgency.

Cases of syphilis, a mandatory reportable disease, are on the tendency of increase, while cases of genital chlamydial infection and gonorrhea, which are sentinel reportable diseases, are decreasing in all districts (Appendix).  Comparing with the complete surveys of the patients conducted in some prefectures, it has been pointed that the current sentinels are insufficient to grasp occurrence among young people (the study group of MHLW) and careful evaluation seems necessary.  To proceed with further control measures to STD involving HIV infection, revision of placement of sentinels and other fundamentals, enabling the surveillance system to grasp more accurately actual conditions of each district, is proposed.

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