The Topic of This Month Vol.19 No.9(No.223)

Current trends of sexually transmitted diseases in Japan

The surveillance for sexually transmitted diseases (STD) complying with the National Epidemiological Surveillance of Infectious Diseases (NESID) was started in 1987. The target STDs counted were five until 1997 (see Table 1 and Fig. 1); since January 1998, syphilis has been included. Information on STD patients is being collected from approximately 600 sentinel clinics and hospitals set up in every prefecture and designated city. The STD sentinels comprise urology, obstetrics and gynecology, dermatology, and STD clinics. In nine of the 47 prefectures, no sentinel is hanging out a shingle of obstetrics and gynecology*.

The total reports of STD patients numbered 44,470 in 1987 when the STD surveillance was started. Since then, the number of patients has varied from year to year, but it was kept on the 40,000 level until 1993, when it decreased to approximately 33,000 due to a marked decrease in gonorrhea patients. The decreasing tendency was kept until 1995, when it turned to an increasing tendency again during 1996-1997 (Table 1). This article deals with the trends of the three important STDs since 1993.

Gonorrhea: The number of reports of gonorrhea patients reached a peak in 1991 after the start of the STD surveillance and then decreased to 40% of that at the time of the peak by 1994. This was regarded as an influence of the campaign of prevention of AIDS accompanying the increase in AIDS patients at that time. Nevertheless, gonorrhea patients changed to increase again in 1995 and were continuously increasing during 1996-1997 (Fig. 1). Therefore, the ratio of gonorrhea patients to all STD patients changed from 19% in 1994 to 25% in 1997 (Table 1). The trend of occurrence of gonorrhea patients by sex and age after 1993 is shown in Fig. 2a. Male patients aged 25-34 years increased slightly also in 1994. During 1996-1997, patients of all ages but those over 60 years increased, particularly the increase of those aged 20-34 was conspicuous. A slight increase in female patients aged 20-24 years was seen during 1996-1997. For the trend of sensitivities of Neisseria gonorrhoeae to the principal antibiotics, see an accompanying article of this issue (p. 201).

Genital chlamydial infection (GCI): The reports of GCI patients showed a tendency of gradual increase after the start of the STD surveillance, but the increase somewhat slowed down during 1992-1995. During 1996-1997, however, a tendency of increase was again shown (Fig. 1). During the same period, the ratio of GCI patients to gonorrhea patients reduced due to the increased gonorrhea patients. The ratio of GCI patients to all STD patients exceeded 45% in 1997 (Table 1). The trend of occurrence of patients by sex and age after 1993 (Fig. 2b) tells that male patients aged 24 years or younger tended to increase gradually. GCI patients of all age groups but that of 40-44 years increased in 1997, particularly the increase in the age groups of 20-24 and 30-34 years is apparent. The peak age group of male patients was 25-29 years until 1996; it shifted to 20-24 years in 1997. Female patients younger than 39 years decreased slightly in 1995 but turned to increase again after 1996. The peak age group of female patients was 20-24 years, and among those under this age group, female patients outnumbered male patients (see IASR, Vol. 11, No. 9, 1990; Vol. 14, No. 8, 1993; Vol. 17, No. 10, 1996).

According to IASR, reports of isolation of Chlamydia trachomatis from genitourinary sources by PHIs during 1993-1997 numbered 1,151. C. trachomatis isolates were serotyped in some PHIs; the trend of serotypes by year is shown in another accompanying article (see p. 203 of this issue).

Genital herpes: Reports of genital herpes patients showed a tendency of slight increase during 1989-1996, but slightly decreased in 1997 (Fig. 1). The ratio of genital herpes patients to all STD patients was 18% in 1996; it decreased to 17% in 1997 (Table 1). The trend of occurrence of genital herpes patients by sex and age after 1993 (Fig. 2c) tells that male patients showed a tendency of decrease except those of age groups of 35-39 years and of over 55 years. On the other hand, female patients of all age groups showed a tendency of no marked change or rather increasing. Occurrence of female patients under 29 years of age was higher than that of male patients of the corresponding age group.

During 1993-1997, reports of isolation of herpes simplex virus (HSV) from genital sources sent to IASR from PHIs and some commercial diagnostic laboratories numbered 282. Fig. 3 shows the types of HSV isolated from 272 patients arranged by sex and age excluding 10 of unknown age. About 80% of HSV-isolated patients were females. This ratio is different from the sex ratio of genital herpes patients presented by NESID. Of HSV isolates, type 2 doubled type 1 in number among male origins, and type 1 and type 2 were the same number among female origins. From patients aged over 60 years, most isolates from both sexes were type 2, indicating that the occurrence of genital herpes in this age group is due to recurrence.

Update: According to NESID information, on the assumption that the number of STD patients during January-June of 1996 was 100, it increased apparently to 106 and 109 during the same period of 1997 and 1998, respectively. Particularly, gonorrhea and GCI patients both increased by 18%. To the contrary, genital herpes patients of both sexes slightly decreased in this year, as did so in 1997.

*Footnote: In line with the amendment of the Communicable Diseases Prevention Law, location of sentinels will be reconsidered.

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