The Topic of This Month Vol.23 No.7(No.269)

Hepatitis B and C in Japan as of May 2002

(IASR 2002; 23:163-164)

If a baby is infected from its mother at parturition with hepatitis B virus (HBV), it will tend to become an asymptomatic virus carrier (carrier) and further has a risk to develop cirrhosis and liver cell carcinoma when grown up.

Introduction of HBV screening of donated blood and common use of disposable needles and syringes for prevention of serum hepatitis have both markedly decreased horizontal transmission of hepatitis B via blood in Japan. Furthermore, owing to the Vertical Hepatitis B Transmission Prevention Project having begun in 1985, development of carriers through mother-to-child vertical infection has been on the dramatic decrease (see IASR, Vol. 21, No. 4).

The studies on hepatitis C virus (HCV), having started with development of reagents for titration of antibodies to HCV in 1989, have disclosed that HCV-infected patients develop chronic hepatitis and some of them progress into cirrhosis and liver cancer, and therefore planning countermeasures for hepatitis C is urgent.

In the National Epidemiological Surveillance for Infectious Diseases (NESID) under the Law Concerning the Prevention of Infectious Diseases and Medical Care for Patients of Infections enacted in April 1999, hepatitis B and C are listed under acute viral hepatitis of category IV notifiable infectious diseases and all physicians are obliged to notify the cases (see IASR, Vol. 21, No. 4). Notifiable diseases include only acute hepatitis due to recent infection; chronic liver diseases, carriers or acute aggravating cases infected in the past are excluded (see p. 170 of this issue concerning the guideline for notification).

Countermeasures for transfusion hepatitis: In late 1960s, the blood collecting system from paid donors was changed to the blood-donating system from volunteer donors. In 1972, HBs antigen screening of donated blood was introduced. Since 1989, tests for HBs antigen, HBc antibody and HCV antibody have been conducted on donated blood and plasma for production of plasma derivatives (Fig. 1). In October 1999, the nucleic acid amplification test (NAT) was introduced for testing HBV, HCV and HIV-serologically negative specimens of all donated blood. NAT has shortened the window period (the undetectable period by the test after infection) and reduced the reports of HBV infection due to transfusion to one fifth of that before introduction, and there have been no reports of HCV nor HIV infection (see p. 165 of this issue).

Urgent countermeasure for hepatitis C: In Japan, deaths due to malignant neoplasm of the liver or intrahepatic bile ducts and from cirrhosis are on the increase yearly (Fig. 2). On the other hand, notable progress has been made in the treatment of hepatitis C by using interferon and ribavirin, which is an antiviral agent (see p. 167 of this issue), making it possible to suppress development of cirrhosis and liver cancer. However, the Meeting of the Learned about Measures against Hepatitis (March 2001) pointed that a large number of patients are unaware of their infection due to the absence of subjective symptoms and that there are possibilities of shifting over to cirrhosis and liver cancer. In response to the council, the Ministry of Health, Labour, and Welfare has made it possible since April 2002 for the people to receive tests for hepatitis viruses in the regular health examinations under the Health and Medical Service Law for the Elderly, health check-up tests for life-style related disease (adult disease) prevention in the government-managed health insurance, or tests for sexually transmitted diseases or HIV antibody (see p. 168 of this issue). It is recommended that all those who have not been tested for hepatitis viruses should receive tests.

National Epidemiological Surveillance for Infectious Diseases: Table 1 shows acute viral hepatitis patients reported after April 1999. Reports of hepatitis A, B and C were all on the decrease in 2000-2001 compared with those in 1999. No case of hepatitis D appeared, and two cases of hepatitis E were reported in 1999 and additional four cases in 2000.

As for hepatitis B, one or two cases of fulminant cases are seen every year and one to three deaths before reporting (Table 1). Age distribution of cases by gender (Fig. 3) shows that there were more males also in 2000 and 2001, and cases aged 20s were the largest in number in either gender as was the case in 1999 (see IASR, Vol. 21, No. 4). As the estimated mode of infection, the rate of sexual contacts have been on the increase; 42% in 1999, 46% in 2000, and 55% in 2001. Continued education for prevention of hepatitis as a sexually transmitted diseases together with HIV seems important. Hepatitis B can be prevented by vaccination; sex partners of carriers, hemodialysis cases, medical staffs, and ambulance staffs can be vaccinated on a voluntary basis.

Since reports of asymptomatic cases of hepatitis C decreased for unknown reasons during 1999-2001, there was some change in the age distribution of cases (Fig. 4). Although the source and route of infection estimated by the physicians notifying the cases were mostly unknown, sexual contact, transfusion, and intravenous drug abuse were mentioned. Others included nosocomial infection, hemodialysis, accidental needle stick, tattoo, acupuncture, and piercing. In 2000, probable outbreaks due to hemodialysis, nosocomial infection and intravenous drug abuse were reported.

At the time of reporting, the route of infection was unknown but later investigation could find out nosocomial infection. Therefore, the route of infection must further be investigated and early notification and thorough countermeasures for nosocomial infection seem important for preventing the spread of infection.

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