Epidemiology of viral hepatitis C: Road to elimination in Japan

Abstract

Although HCV infection was the main cause of HCC in Japan contributing 70% over two decades after its first cloning in 1989, it was markedly decreased to 49% in 2013 and expected to decrease continuously. Based on blood donor national database, the new incident cases were 0.4/100,000 person-years, the prevalence was 0.13% and the total number was 890,902-1,302,179 in 2015. Establishment of blood donor screening with anti-HCV measurement and nucleic acid test introduced by Japanese Red Cross as pioneer, high-level medical and surgical care, and the government's policy under the Basic Act on Hepatitis Control have changed its epidemiology and outbreak trend and also enforced the disruption of potential transmission cascades. HCV prevalence among the younger generation was extremely low in all regions, and the predominant age for HCC has shifted to over 60 years old population. Considering such changes, HCV induced HCC occurrence is supposed to be ultimately suppressed in the near future. However, taking into account society changes, regulating intravenous drugs users and monitoring high-risk groups such as tattoos, and men who have sex with men are indeed required in Japan. Understanding the epidemiological changes in HCV is important in assigning, modifying, and designating effective response systems. Selective or national action plans, strategic approaches, and cooperation between government sectors have a positive impact on HCV prevention and control. A dramatic decrease in total number of HCV carriers, increase in number of people treated with highly effective DAA, and subsequent high SVR indicates Japan might achieve WHO's target of HCV elimination by 2030.

Keywords: Japan; countermeasure; disease burden; elimination.

Figure 1.

HCV prevalence trend among first time blood donors and its corresponding countermeasure in Japan. In the figure, the red line shows the prevalence of anti-HCV among first time blood donors since 1995. The decreasing trend was illustrated by line and each countermeasure was stated with corresponding arrow indicating the implemented year.

Figure 2.

Natural course of HCV infection in hypothetical cohorts aged 40 years until they reach 70 years of age. It shows the transition probabilities and the natural course of HCV infection in those who were diagnosed with HCV induced chronic hepatitis at the age of 40 and then turned into 70 years old. The starting point is defined at 40 years old who were first diagnosed as chronic hepatitis.

Figure 3.

Age-specific prevalence of anti-HCV among first-time blood donors during 2012-2016. In this figure, Japan is geographically divided into eight main regions and the age specific prevalence of anti-HCV is shown for each region in the bar graph and each color in the map represents its corresponding region.

Figure 4.

Trend of HCV Incidence among blood donors. This figure represents the incidence rate of anti-HCV among blood donors in Osaka (1992-19797), Hiroshima (1992-1995 and 1994-2004) and all of Japan (2008-2013). The reduction of the incident cases is indicated by the red arrow.

Figure 5.

Trend of HCV carriers in Japan during 2000-2015. This figure simply presents the number of HCV carriers by their liver disease status in 2000 and 2011. Each colored bar represents each liver disease status, in order, Total number of HCV carriers, Undiagnosed HCV carriers, Patients taking medical care as in or outpatients at health facilities, and the un-consulted patients who never visit or were lost to follow-up after being diagnosed as HCV carriers. For 2015, the patients are shown in two subcategories: dark brown bar for those taking antiviral treatment and light brown bar for those not taking any antiviral treatment.

Figure 6.

Contribution of HBV, HCV and others to HCC related deaths in Japan. This figure describes the contribution of HBV, HCV and others to HCC related deaths in Japan. The orange bar represents HBV, the green bar HCV, the light blue bar non-A non-B and the dark blue bar non B non C.