Infectious Disease Fight Against Infectious Diseases

During early Meiji era in Japan, there were frequent epidemics of fatal acute communicable diseases such as cholera, dysentery and smallpox, and preventive measures and preparations for acute infectious diseases were urgently needed. Together with improvement of scientific preparations, the Communicable Disease Prevention Law was promulgated in 1897. Then gradually until 1940's, the focus of preventive measures have been shifted from acute infectious diseases to chronic ones, particularly tuberculosis. After the World War II, except the short period of social confusion, major legally-defined communicable diseases had been decreasing rapidly mainly due to the use of antibiotics and improvement of environmental sanitation. At the same time, the introduction of preventive vaccination marked a new era for the prevention of infectious diseases and was largely responsible for the remarkable decrease of infant mortality in Japan. Recently the concept of defense by vaccination against infectious diseases has evolved from group-oriented to individual-oriented, so that the Preventive Vaccination Law was drastically revised in 1994. Currently, effective counter-measures against newly emerged infectious diseases, as viral hepatitis, institution-acquired infection, viral hemorrhagic fever etc., have been implemented. For the future, improvement of infections disease surveillance, vaccine development and expansion of vaccination coverage along with monitoring sideeffects, preventive health education on AIDS/STDs, addressing the special needs of foreigners living in Japan and international collaboration for disease control abroad are all vital to the success of protection of the public's health from infectious diseases in Japan. J Epidemiol, 1996 ; 6 : S61 -S66.


Fight Against Infectious Diseases
Kenji Soda1, Mitsuhiro Kamakura2, and Katsuhiko Kitamura1 During early Meiji era in Japan, there were frequent epidemics of fatal acute communicable diseases such as cholera, dysentery and smallpox, and preventive measures and preparations for acute infectious diseases were urgently needed.
Together with improvement of scientific preparations, the Communicable Disease Prevention Law was promulgated in 1897.Then gradually until 1940's, the focus of preventive measures have been shifted from acute infectious diseases to chronic ones, particularly tuberculosis.
After the World War II, except the short period of social confusion, major legally-defined communicable diseases had been decreasing rapidly mainly due to the use of antibiotics and improvement of environmental sanitation.
At the same time, the introduction of preventive vaccination marked a new era for the prevention of infectious diseases and was largely responsible for the remarkable decrease of infant mortality in Japan.
Recently the concept of defense by vaccination against infectious diseases has evolved from group-oriented to individual-oriented, so that the Preventive Vaccination Law was drastically revised in 1994.Currently, effective counter-measures against newly emerged infectious diseases, as viral hepatitis, institution-acquired infection, viral hemorrhagic fever etc., have been implemented.For the future, improvement of infections disease surveillance, vaccine development and expansion of vaccination coverage along with monitoring sideeffects, preventive health education on AIDS/STDs, addressing the special needs of foreigners living in Japan and international collaboration for disease control abroad are all vital to the success of protection of the public's health from infectious diseases in Japan.J Epidemiol, 1996 ; 6 : S61 -S66.

BRIEF HISTORY OF THE FIGHT AGAINST INFECTIOUS DISEASES AFTER THE MEIJI RESTORATION (1868) IN JAPAN
Preventive measures against infectious diseases are among mankind's greatest achievements.The outline of the progress in Japan is summarized in Table 1.The Bureau of Health at the former Ministry of Home Affairs was organized in 1875.There were severe epidemics of cholera, dysentery and smallpox at that time in Japan.Preventive measures for acute infectious diseases were urgently needed.The Private Health Association of Japan was founded in 1883, and the Research Institute for Infectious Diseases (the present Institute of Medical Science, University of Tokyo) was organized in 1892.After these scientific preparations, the Communicable Disease Prevention Law was promulgated in 1897.Early in the twentieth century, the expansion of industrialization, the concentration of population in big cities and the improvement of environmental sanitation brought about the change of objects in preventive measures from acute infectious disease to such chronic ones as tuberculosis and leprosy.The original Tuberculosis Prevention Law was enacted in 1919 and was drastically revised in 1951 to the present form.During the period of social confusion following the World War II, temporary widespread epidemics of acute infectious diseases prevailed.However, the enactment of the Food Sanitation Law, the Preventive Vaccination Law, the Venereal Disease Prevention Law and the new Tuberculosis Prevention Law helped to address the problems.Together with the economic reconstruction after the war, including improvement of sanita-

THE RECENT TREND OF INFECTIOUS DISEASES IN JAPAN
Legally-Defined Specially-Designated and Notiiable Communicable Diseases Among all infectious diseases, 11 legally-defined communicable diseases, 2 specially-designated communicable diseases and 13 notifiable communicable diseases are designated as diseases with necessary administrative preventive measures outlined by the Communicable Disease Prevention Law.The details of the three categories are shown in Table 1.Acute poliomyelitis belongs to two categories.As to the recent trend of these infectious diseases the reported number of legallydefined communicable disease cases is very small.The diseases which had a relatively large number of cases reported in 1994 were dysentery (1,042cases), cholera (90cases), typhoid fever (7lcases) and paratyphoid fever (49cases).Most of them were contracted abroad.The reported number of cases of notifiable communicable diseases is generally decreasing except for influenza and tsutsugamushi disease.After the World War II, the incidence of tsutsugamushi disease decreased markedly to one digit until the 1970's.But the incidence has increased again since around 1980 and, recently, almost 1,000 cases are reported every year.In addition to the cases reported under the law, the actual incidence of influenza and measles are checked by the infectious disease surveillance system which is discussed later.Judging from the surveillance report, the preventive effect of the vaccination program for influenza has been less than desired 1).

Tuberculosis and Leprosy
After the introduction of anti-TB drugs and BCG vaccination, the incidence and the number of registered cases of tuberculosis (including atypical mycobacteriosis) have decreased markedly.These preventive measures had the largest effect on the decrease of the incidence in children and young adults under 30 years.But the death rate (2.6 per 100,000 population in 1993) still remains relatively high, compared with the United States, and with European countries.It is noted that the decrease in the incidence of tuberculosis has recently leveled off.Group outbreaks are also sometimes reported, and are most frequent among high school students and foreign residents.The details are described in a following section.
The prevalence of leprosy is 5.2 per 100,000 persons in 1994.About 40~60% of the new cases have been reported from Okinawa Prefecture in the last ten years.The average age of those hospitalized at 13 national and 2 private leprosariums has gradually increased to 67 years old in 1994.In the past two or three years, the number of newly reported cases of leprosy was around ten, and the Leprosy Prevention Law was repealed in March, 19961).

Imported Infectious Diseases, Parasitosis and International Communicable Diseases
Due to the increase in the number of international travelers, the reported number of imported infectious diseases has increased in Japan.An increasing number of Cholera (El Tor Ogawa vibrio) cases infected abroad has been reported since the end of the 1970's to account for about 80% of the reported cases.A large amount of the typhoid and paratyphoid fever and bacillary dysentery are imported cases, i.e., on average, about 40% and 60% respectively in the 1990's.Malaria cases are mainly those contracted in Asia.The recent appearance of the protozoa which is resistant to chloroquinine and fansidar is a problem to be taken seriously.Because of the eradication of Japanese schistosomiasis and marked decrease of other enteric parasitosis, the Parasitosis Prevention Law was repealed in 1994.But a different type of parasitosis has been reported since then.Nearly one thousand cases of anisakiasis are observed every year, because the Japanese have recently had an abundant opportunity for eating raw sea-fish and shellfish.The increase of echinococcosis, a fecal-oral infection from Vulpes vulpes (the North fox), is reported in Hokkaido, and threatening an invasion of the Main Island of Japan.
In 1976, five Japanese tourists who boarded the same aircraft as a patient with Lassa fever were placed into isolation.Again in 1987, a Japanese tourist returning from Sierra Leone, who was suspected as having Lassa fever, was kept in an isolation hospital.These cases were concrete and dramatic evidence that domestic control measures alone were not enough for the prevention of infectious diseases in Japan.Four kinds of viral hemorrhagic fever, i.e., Lassa, Ebola, Marburg and Crimean-Congo hemor hagic fever, are listed as the international communicable diseases.Highly-protected hospital wards were set up in the Metropolitan Ebara Hospital, and highly-protected laboratories for early detection of these diseases were established in the National Institute of Health.But further preparation and reinforcement of the total prevention system against these infectious diseases are vitally necessary2).3).and Sexually Transmitted Diseases (STDs) Currently in Japan, 50% of reported AIDS cases and 42% of known HIV carriers are those infected from blood products.Excluding the cases infected through non-heat-treated blood coagulants, about 70% of the infection is from sexual contacts including the cases of men who have sex with men.In the beginning, the location of contracting HIV was mainly in Western countries and Southeast Asia.However among Japanese, the ratio of domestically-acquired HIV infection has been increasing and now accounts for about 60%.The details are described in a subsequent section5).Four STDs (syphilis, gonorrhea, chancroid and lymphogranuloma inguinale) that the Venereal Disease Prevention Law covers, have been generally decreasing.About three quarters of the reported cases of STDs are gonorrhea, and, unfortunately, the proportion of penicillinresistant gonococci is increasing.According to STD surveillance, the leading STD is genital Chlamydiasis which is gradually increasing1),4).Therefore, the prevention of STDs includ-ing HIV/AIDS, particularly through the wider distribution of preventive health education, should be a high priority.

Viral Hepatitis
The main target of preventive measures for viral hepatitis are hepatitis A (HAV), hepatitis B (HBV) and hepatitis C (HCV).The average age of anti-HAV antibody positives has gradually increased.In other words, the population that has no herd immunity is increasing.In 1985, 50% of those under age 42 have no HAV antibody.This implies the importance of preventive vaccination for travelers to areas of high HAV prevalence.The number of HBV carriers is decreasing as a result of the screening of donated blood since 1972 and the use of disposable medical apparatus.However the estimated number of HBV carriers is 1.2~1.4 million and larger than that in Western countries.The vertical transmission cases have been markedly decreasing since 1985 as a result of the prevention program for hepatitis B maternal-fetal transmission.The number of asymptomatic carriers of HCV is estimated at 2~3 million, but is surely decreasing as a result of the screening of donated blood, implemented after November 1990 to lower the incidence of post-transfusion hepatitis from over 10% to 2~3%.The surveillance of viral hepatitis and of these carriers is considered to be an important preventive measure, and has been a public health priority since 19871).

Institution-Acquired Infection
By analyzing the distribution of cases, a gradual increase of death related to infection (category A death) was recognized since 1979.The increase proved to be correlated with the increase in death rate from pneumonia.Underlying this increase are the problems of elder people confined to bed, nosocomial infection of MRSA and the increase in number of hospitalized elderly who are a immuno-compromised host.For the lack of an appropriate reporting system, the true level of nosocomial infection has not been fully grasped.It is necessary from now on to implement improved and effective infection control programs in all medical institutions.

Food-Borne Infectious Diseases
Despite of the improvement of environmental sanitation, the incidence of bacterial food poisoning has leveled off.Diversity of food, the increase of imported food and the expansion of the food-service industry are considered to be the reasons.The annual reported number of food poisoning cases is 30,000~40,000.The number of poisoning accidents is decreasing, but the number of cases per accident is increasing for 40~50 cases in the 1990's.Cultural factors have a special role in food poisoning in Japan such that the number of poisonings caused by Salmonella and Vibrio parahaemolyticus from fish and shellfish is rather large1).Currently, Escherichia coli 0 157 : H7 has been noticed as an emerging cause of foodborne illness all over the country.

Cancer-Related Infectious Diseases
The relationship between HTLV-I infection and adult T-cell leukemia (ATL) has been a focus of considerable research in Japan.The virus is known to be transmitted through blood transmission, sexual contact and mother's milk.The geographical distribution of the carriers is mainly in western Japan, and the number is estimated at 1.2~1.4 million.National screening of donated blood has been in place since 1986.Avoidance of breast feeding by antibody-positive mothers is highly effective for vertical transmission prevention.Widespread testing of the population and preventive measures all over the country is considered, however, not necessary, because there is a tendency for the carriers to decrease naturally6).Of the death cases from liver cancer reported in 1988, 21% were HBs antigen positive, 57% were HCVantibody positive and 4% were positive for the both.Hepatitis B and hepatitis C should also be considered important from a viewpoint of prevention of hepatic cancers7).Finally, Helicobactor pylon, living in the stomach, is recently reported as a possible risk factor for gastric cancer, and is a possible focus of future preventive measures.

FUTURE STRATEGIES AGAINST MAJOR INFECTIOUS DISEASES
The future strategies for dealing with infectious diseases in Japan is outlined as follows;

Infectious Disease Surveillance System
Monitoring the trend of both diseases and pathogenic agents are important for the preventive measures of infectious diseases.The Ministry of Health and Welfare therefore introduced the infectious disease surveillance system in 1981.The system is designed to investigate the epidemics of 18 communicable deseases on a weekly basis in all prefectures and large municipalities, with over 3,000 designated clinics and hospitals.In 1987, the number of target diseases for surveillance was increased to 27, including viral hepatitis and typical STDs.And the system also combined the existing tuberculosis surveillance system to change the name to "Surveillance System for Tuberculosis and Other Infectious Diseases" .In the same year, the system was developed into a computerized on-line system to facilitate the communication and analysis of surveillance data on both the incidence and distribution of pathogenic agents.The details are discussed in a subsequent section').
In addition to this surveillance system, the government carries out the predictive surveillance of communicable diseases with the cooperation of prefectural public health laboratories .This work was introduced in 1963, mainly consisting of serological surveys for antibody levels and for the isolation and identification of causal agents.Seven vaccination-preventable diseases, including acute poliomyelitis, influenza , rubella, Japanese encephalitis, pertussis, diphtheria and measles , are the main targets of this survey.

Preventive Vaccination
Preventive vaccination of various communicable diseases has been administered since 1953 under the Preventive Vaccination Law.In 1994, the law was revised drastically from compulsory vaccination to that of encouragement, and voluntary individual-oriented vaccination is currently promoted.An exception to this approach is the vaccination by group for acute poliomyelitis.Some modifications, such as the abolition of MXIR (measles, mumps and rubella) vaccination after 1993 due to many cases of post-vaccination meningitis, and voluntary influenza vaccination, were also introduced (see Table 2).
After discovering a decrease of vaccination coverage rate because of these reforms of the law, the possibility of a subsequent epidemic is a matter of increased concern.The improvement in the safety of vaccines, establishment of a system for monitoring side-effects, and the expansion of community medical facilities in charge of vaccination remain as future objectives.Follow-up procedures for children who missed their vaccinations are a special problem in Japan.Because, in Japan, if a child is brought for vaccination after the recommended age, parents must then pay for it, and consequently, some of them never get the vaccine.Only by solving these problems can a significant improvement in vaccination coverage rate be expected8).
Measures Against the Diseases of Foreigners Living in Japan Domestic infectious disease control measures had to change to adapt to the increase of foreign residents such as foreign workers, students and refugees in Japan.A study on over 3,000 refugees at an immigration camp in 1989 and 1990 reveals that the prevalence rate of intestinal parasites, HBs anti- gen and TB positive X-ray findings are 66%, 22% and 2%, respectively3).National health insurance coverage is not always available for foreign residents, especially for illegal ones under the present medical insurance system in Japan.
Early diagnosis and treatment are therefore more difficult and delayed and their diseases progress farther and faster.For HIV infection in Japan, excluding hemophiliac cases, 30% of AIDS cases and 53% of HIV carriers are foreigners5).For tuberculosis, such problems as the untreated infection of foreign residents, the combined infection of TB with atypical mycobacteria or TB with HIV, constitute a menace to the preventive measures of tuberculosis in Japan.These conditions have to be addressed quickly and effectively to adequately protect the health of the general public.

International Cooperation
International collaboration is a key to development of effective control of infectious diseases.The contribution of Japan to the preventive measures of infectious diseases in other Asian countries is important to maintenance of Japan's public health and is a task that needs to be continued.In 1994, as official bilateral medical cooperation 49 projects of technical cooperation, 12 of which are directly related with infectious disease control, have been implemented in 29 developing countries.An international training institution is now provided in the National Institute of Health and technical education and training in several infectious diseases such as HIV infection and acute poliomyelitis are offered with the cooperation of the Japan International Cooperation Agency (JICA) and International Medical Center of Japan (IMCJ).Recently various training courses for foreigners by some NGOs, such as Japan Anti-Tuberculosis Association and Japan International Cooperation of Welfare Services (JICWELS), has been implemented.This kind of training course will play a very important role in this international effort and should be continued on a permanent basis 9).In summary, improved surveillance, vaccine development, expansion of vaccination coverage with available vaccines, monitoring side-effects, preventive health education on AIDS/STDs, addressing the special needs of foreigners living in Japan and international collaboration for disease control abroad are all vital to the future success of protection of the public's health from infectious disease in Japan.

Table 2 .
Preventive vaccination and target diseases *PreventiveVaccination Law was revised in June, 1994 and the new Law came into effect in October of the same year.