The Topic of This Month Vol.20 No.10(No.236)

Tuberculosis, as of 1998, Japan

In July 1999, the Ministry of Health and Welfare (MHW) proclaimed "Declaration of State of Emergency Concerning Tuberculosis" and proposed to a better understanding of tuberculosis (TB) and the need of coping with intensification of the anti-TB programs. The incidence in Japan increased consecutively from 1997 through 1998 (see p. 240 of this issue). About 44 thousand new cases occur and about 3 thousand people die of TB on a yearly basis. There are about 54 thousand active TB cases nowadays.

The Tuberculosis Prevention Law requires physicians to notify all clinically diagnosed TB patients to the nearby health center within two days (Article 22, the Tuberculosis Prevention Law). Registration of the TB cases is undertaken at the regional health center, covering the residence of the patients. Since 1987, the data on registered TB patients have been reported and tabulated every month and at the end of each year through the computer-network system connecting the health center to the local governments (prefectures and ordinance-designated cities), and to MHW. The Research Institute of Tuberculosis, Japan Anti-Tuberculosis Association (JATA), analyzes the collected data and publishes yearbooks.

The following is a summary of the current status of TB in Japan primarily based on Annual Report on Tuberculosis Surveillance in Japan 1998, press released on September 24, 1999 by the Infectious Diseases Control Division, the Health Service Bureau, MHW in cooperation with JATA.

Numbers of deaths: Deaths of TB in 1998 totaled 2,795 (increased by 53 from 1997) and the annual incidence rate was 2.2 per 100 thousand population (the Vital Statistics of Japan, MHW)(Fig. 1). TB was the top leading cause of death from 1935 (190.8 per 100 thousand) through 1950 (146.4 per 100 thousand), which thereafter decreased toward the 22nd ranking in 1998. The higher is the age, the higher is the death rate.

Numbers of registered cases: Newly registered TB patients counted up 44,016 in 1998 (increased by 1,301 from 1997) and the annual incidence rate (the number of newly registered cases during a year per 100 thousand population) was 34.8 (increased by 0.9 from 1997). Both figures increased for two consecutive years (Fig. 2). The newly registered cases by age group show that those aged 70 years and over numbered 15,850 (increased by 1,146 from 1997), and the incidence rate of this age group was 116.1 per 100 thousand population, indicating an increase in TB cases in the aged. Smear-positive TB patients, that may be discharging tubercle bacilli and serve as the source of infection to other people, counted up 16,294 (increased by 327 from 1997) and the annual incidence rate 12.9 (increased by 0.2 from 1997). Among smear-positive TB cases, those of 70 years of age and over markedly increased, numbering 6,093 (Fig. 3), and accounted for more than one-third of all cases. As of December 31, 1998, TB cases registered to the health centers all over Japan totaled 113,469 (decreased by 8,293 from 1997). Of these cases, the total number of patients with active lung and extrapulmonary TB requiring treatment was 53,714 (decreased by 1,668 from 1997) (Fig. 4). Active pulmonary TB cases accounted for more than 85% of them. Similarly to the case number and incidence rate, the prevalence rate (the number of active TB cases at the end of the calendar year per 100 thousand population) of aged people is high.

Regional difference in TB incidence rate: The incidence rate of TB is high in such prefectures as Osaka (70.1), Hyogo (49.2), and Tokushima (46.2), and low in Nagano (16.7), Fukui (22.5), and Yamanashi (22.7). Like the smear-positive and the prevalence rates, this trend indicates that the TB incidence rate is high in western areas while low in eastern areas (Fig. 5). An increasing tendency of TB cases can be seen in urban districts. The incidence rates of urban districts are high, being 106.7 for Osaka City (increased by 2.9 from 1997), 57.6 for Kobe City (decreased by 7.2), 45.0 for Nagoya City (decreased by 0.3), 43.3 for Kyoto City (increased by 3.4), and 41.0 for Kita-Kyushu City (decreased by 2.2). The incidence rate by health center in 1997 is the highest, being 506.6, for Nishinari Health Center (HC), Osaka City, followed by Naniwa HC in Osaka City (260.7), Hyogo HC in Kobe City (116.2), Taito HC (106.0) and Shinjuku HC in Tokyo (99.0). TB is a serious problem in particular sites of big cities, where homeless and unemployed single people tend to gather.

Outbreaks of infection with tubercle bacilli: An outbreak of TB infection is defined as a cluster of Mycobacterium tuberculosis infections in more than two families involving more than 20 infected persons exposed to a common source. In counting infected persons, the occurrence of a symptomatic patient with TB is regarded as equivalent to six individuals infected with tubercle bacilli. Recently, outbreaks of TB infection occurring in schools and medical facilities have been reported (15 in 1995, 20 in 1996, 42 in 1997, and 44 in 1998; three nosocomial infections in 1995, nine in 1996, seven in 1997, and 11 in 1998), showing an increasing tendency. We must pay attention to the fact that nosocomial TB infection occurs in hospitals both with and without beds for TB patients.

Drug resistance: Multidrug-resistant M. tuberculosis is defined as that resistant simultaneously to isoniazid (INH) and rifampicin (RFP), which constitute the kernel of antimicrobial chemotherapy. Multidrug-resistant TB patients are estimated at about 1,500-2,000 and annual new cases about 80 in Japan. The increased multidrug-resistant TB cases suggest the returning of the anti-TB programs to the age before development of anti-tubercle drugs. Thus, multidrug-resistant M. tuberculosis is a worldwide problem (see p. 240 of this issue).

The world-wide status: In 1997, a total of 3,368,879 TB patients were reported to the World Health Organization (WHO) from 173 countries (58 per 100 thousand population). The smear-positives of these patients totaled at 1,292,884 (38%) (see p. 249 of this issue). In the whole world, it is estimated that 8 million people get TB and 3 million people die of TB every year, and there are 22 million active TB patients at the moment. In April 1993, WHO proclaimed the critical global TB emergency and declared that TB is a menace to the whole world.

Conclusion: In Japan, TB control is being undertaken in compliance with the Tuberculosis Prevention Law and has been systematized with such kernels as medical examinations, prevention, case management, medical service for TB patients, surveillance for TB, special project for regional difference in TB prevalence. In Japan, the following problems seem at a level of a must be solved.

1) Decreased attention to TB among the general public, medical staffs, and central and local governments.
2) Lowered ability of clinical doctors to diagnose TB.
3) Increase in aged TB patients.
4) Regional difference in prevalence.
5) Increased outbreaks of TB infection.
6) Emergence of multidrug-resistant TB.

Furthermore, the research on and development of simple, rapid and specific tests for detection of M. tuberculosis infection is strongly needed.

From this point on, it is necessary to recognize the importance of TB as a re-emerging infectious disease and to promote strategies for TB prevention and control by applying complete treatment to eliminate the source of infection.

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