The Topic of This Month Vol.20 No.4(No.230)

HIV/AIDS Surveillance in Japan as of December 31, 1998

The National AIDS Surveillance Committee, the Ministry of Health and Welfare, holds committee meetings every other month to make confirmation of cases of HIV-infected persons without AIDS (hereafter abbreviated to HIV cases) and AIDS patients reported by means of individual cards (excluding those infected by the use of coagulation-factor products). The Committee keeps track of the incident trends, which are published periodically. The HIV/AIDS reporting system and the method of analyzing the information in Japan were described in the 1997 report (see IASR, Vol. 19, No. 4). The following is a summary of the up-to-date information of HIV/AIDS surveillance compiled by the National AIDS Surveillance Committee after analyzing all data obtained during 1985-1998.

1. Incidence of HIV/AIDS in 1998

The reported HIV cases numbered 422 and AIDS patients 231 in 1998. Sexual contacts were the most common mode of infection, accounting for 74% of HIV cases and 65% of AIDS patients. In comparison with the nationalities and sex, Japanese male cases were the largest in number, accounting for 62% of HIV cases and 68% of AIDS patients (Fig. 1). The male:female ratio was about 3:1 among HIV cases and about 6.5:1 among AIDS patients. The greater part of Japanese cases were of domestic infection (75% of HIV cases and 65% of AIDS patients) (Fig. 2). The largest number of infections were reported in Kanto/Ko-shinetsu district including Tokyo (75% of HIV cases and 74% of AIDS patients), followed by Kinki district including Osaka (12% of HIV cases and 8.2% of AIDS patients).

2. Comparison with the reports in 1997

HIV cases in 1998 showed an increase of 25 cases from those in 1997 and were the largest number of yearly reports since 1993. In both years 1997 and 1998, Japanese male cases of domestic infection through sexual contacts were large in number, especially HIV cases caused by homosexual contacts. The reports of HIV cases increased from the preceding year in Hokkaido, Tohoku, Kanto/Ko-shinetsu (excluding Tokyo) and Kinki districts.

As compared with HIV cases, the yearly reports of AIDS patients turned to decrease in 1998, nevertheless reports on AIDS patients from homosexual contacts among Japanese males increased. It is not clear whether the decreased reports of AIDS patients were due to the effects of the multi-drug combination therapy with anti-HIV drugs that have often been used recently, or some other reasons.

3. The cumulative reports and the trend of incidence from 1985 through December 31, 1998

a) According to Fig. 3, the yearly reports of HIV cases decreased after a sharp increase in 1992, but continued to increase after 1995. The yearly reports of AIDS patients continued to increase until 1997, but, as stated above, they turned to decrease for the first time in 1998. The increase in HIV cases reflected the increase in Japanese male cases of domestic infection. Japanese female, non-Japanese male or female cases did not change in number or rather tended to decrease during the past five years. Non-Japanese cases accounted for about 30% of both HIV cases and AIDS patients in 1998. During the past five years, non-Japanese HIV cases tended to decrease gradually, whereas AIDS patients maintained on the same level, being about 30-50% of the total.

b) The cumulative numbers of reports until December 31, 1998 were 2,913 for HIV cases and 1,286 for AIDS patients. In addition, cases of infection due to the use of coagulation-factor products were confirmed by the nation-wide surveillance (1,434 HIV cases and 631 AIDS patients as of July 13, 1998). Regarding the mode of infection other than by the use of coagulation-factor products, HIV infection by sexual contact was the most predominant (48% for heterosexual and 24% for homosexual contacts). Cases of infection due to intravenous drug abuse and of mother-to-child infection were rare, both accounting for 0.7% (Fig. 4). Similar ratios were shown with AIDS patients.

The results of analysis according to the mode of infection clearly show that Japanese HIV cases are markedly increasing among males through homosexual contacts and that cases of unknown mode of infection are also tending to increase (Fig. 5a). The ratio of the latter cases reached about 16% in 1998. There are a large number of cases of unknown mode of infection particularly among non-Japanese, accounting for about 40% of non-Japanese HIV cases every year (Fig. 5b). Moreover, about 50% of non-Japanese and more than 20% of Japanese AIDS patients are of unknown mode of infection.

c) As for the place of infection, it is noteworthy that Japanese male HIV cases of domestic infection and of unknown place of infection are increasing, and cases of infection in Japan of non-Japanese also tends to increase.

d) The results of analysis for geographical distribution of non-Japanese cases staying in Japan indicate that the largest number of both HIV cases and AIDS patients came from South and Southeast Asia followed by those from Latin America and sub-Saharan Africa.

e) Concerning the age distribution, the largest number of HIV cases were at the age between 25 and 34 years in males and between 20 and 29 years in females regardless of the nationality. AIDS is particularly prevalent among Japanese males at the age of 40 to 49 years and Japanese females at the age of 25 to 39 years.

f) Distribution of each AIDS-defining disease was examined with cumulative reports of AIDS patients of Japanese and non-Japanese (925 and 361, respectively) as the denominator. Similar distribution was found between the two groups; Pneumocystis carinii pneumonia was most frequent, accounting for about 40% and candidiasis and wasting syndrome due to HIV accounted for in between 10 and 20%. A difference was seen in active tuberculosis; non-Japanese cases were twice as many as Japanese ones, accounting for 14 and 6.7%, respectively.

g) The HIV-antibody-positive rate of blood donors reached 0.9 per 100,000 donations for the consecutive 1997 and 1998, indicating that there are still many blood donors with the purpose of HIV testing or not aware of HIV infection. Under such circumstances, blood donation at the window period is anticipated.

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