Study On The Epidemic Trend And Forecasting Of The Main Communicable Diseases In Shandong Province

Communicable diseases own the characteristics of communicability which are caused by pathogenic microorganism and parasitic infection. Because of its "communicability" and "epidemicity", it is still one of the diseases which are influence human health seriously. According to the reports of WHO, 40 are infectious diseases and verminosis among 48 diseases which are most harmful to human beings; in 1995, 17 million patients died from infectious diseases among 52 million mortality. STD( Sexually transmited disease), viral hepatitis and upper-trachea infection are the most common diseases in developed countries; in most developing countries, infectious diseases are even more hazardous, and still main diseases causing death. Since the establishment of PRC, great progress has been made in prevention and treatment for infectious diseases under the policy of "Putting prevention first & Combining prevention with treatment". So far, the most common diseases are viral hepatitis B, HFRS and measles in Shandong province, and they are still the main diseases which should be prevented and control. In addition, in some depressed area, the fatalness of outbreak and epidemic of some infectious diseases still exist due to lack of health resource. Therefore, in order to supply scientific support for the government to take measures to prevent and control infectious diseases, it is necessary to explore the epidemiology of the most harmful infectious diseases in Shandong province. The study based on the epidemic materials of 19 infectious diseases in Shandong province between 1963 to 2005,include: (1)analyzing the epidemic trend and seasonal characteristics of 19 infectious diseases in Shandong province using descriptive epidemiological methods; (2)exploring the spacial distribution characteristics of viral hepatitis B, HFRS and measles in Shandong province among different period using GIS technics; (3)selecting different predictive methods to predict the incidence of viral hepatitis B, HFRS and morbilli, according to their epidemic trend and seasonal characteristics.The Main Results:1. General situation of the incidence rate of 19 kinds of legal infections from 1963 to 2005 in Shandong Province(1)The average incidence rate of 19 kinds of legal infections decreased from 3918.09/100,000 in 1960s to 45.91/100,000 in 2000; in 43 years, there were two peaks, one occurred in 1964 with incidence rate of 6417/100,000; the second one was in 1971 with accidence rate of 11282/100,000; During the 1970s to 1980s, the total incidence rate of legal infections decreased distinctly; after 1998, the total incidence rate of legal infections were stable, keep with a lower level.(2) During the 1960s to 1970s, the respiratory infections took the first place, respectively accounting for 51.49% and 53.72%; from 1980s to 2000, it was mainly intestinal infections, respectively accounting for 67.04%, 80.19% and 80.89%; the spectrum of disease of top five infectious changed in different year, in specific, in 1960s, the infectious were mainly malaria, flu, measles, dysentery and epidemic meningitis, but in 1990s, the spectrum of infection was mainly hepatitis B, hemorrhage fever, measles, typhoid and scarlet fever, but the incidence rate of typhoid and scarlet fever was only respectively 0.62/100,000 and 0.59/100,000.2. General situation of the incidence rate of 3 kinds of the main infections from 1963 to 2005 in Shandong Province(1)Viral Hepatitis: Unsubtyped period (1963-1989):①the incidence rate was comparatively low in 1960s (45.04/100,000) and began to rise after 1970s - the mean incidence rate was 111.37/100,000; (2) one of the characteristics is the periodicity -a peak of incidence occurred in about 4-5 years; in 27 years there were totally 5 peaks of incidence among which the incidence rates in 1972 and 1977 were the highest -separately 284.95/100,000 and 464.13/100,000 (3) there was no seasonal variation in 1960s in the incidence of Viral Hepatitis and after 1970s an obvious seasonal variation occurred - the peak of incidence was autumn and winter; (4) there was Viral Hepatitis all over the province but the spatial distribution was distinctly different in different years. Subtyped period (1990-2005): (1) there was a downtrend in the incidence of Hepatitis A which decreased from 45.34/100.000 in 1990 to 1.53/100,000 in 2005; there was an upward trend in the incidence of Hepatitis B which rised from 13.02/100,000 in 1990 to 43.06.100,000 in 2005; in 1990 there was an intercross in the curves of incidence rate of Hepatitis A and Hepatitis B .(2) there was a seasonal variation in the incidence of Hepatitis A: the incidence rates in spring (from March to May) and autumn (October and November) were higher than in other months; there was no distinct seasonal variation in the incidence of Hepatitis B. (3)in 1990s, it is higher than in 2000s from the incidence area and level of the HAV, the incidence rate were highest in Qingdao and Jinan; While the area obviously enlarged of HBV in 1990s, and the incidence rate was highest in Jinan and Zibo. After 2000, the epidemic level is higher than in 1990s, and the highest area are Weihai.(2) Hemorrhagic fever with renal syndrome (HFRS): (1) The incidence rate was extremely low in 1960s, however, it gradually increased after 1970s, and there were two peaks of incidence rate (outbreak of epidemic ) in 1986 and 1995, the incidence rate were 52.56 per 100, 000 population and 26.05 per 100, 000 population, respectively. After 1998, the incidence rate tended to downwards, and the incidence rate had stabilized from 11.4 per 100, 000 population to 2.39 per 100, 000 population since 2000, which showed scattering outbreak. (2)The incidence rate of HFRS in Shandong province obviously fluctuated according to season, and it was different between every two decades. The incidence rate was low in 1970s, and it mainly distributed in autumn and winter (from October to February of secondary year), which was simple autumn-winter peak. The incidence rate obviously increased in 1980s, and there were two peaks, autumn-winter peak (from October to February of secondary year) and spring peak (from March to May), and the autumn-winter peak was the main one. The incidence showed slight downtrend in 1990s, and there were two peaks, but the' spring peak was the main one. After 2000, the incidence rate obviously decreased, but the seasonal distribution was similar to that in 1980s on the whole. (3)There were cases only in Jining area in 1960s, the epidemic areas of infectious disease were localized in Linyi and Weifang in 1970s, and the area obviously enlarged, almost the whole province was involved, and the incidence rate were highest in Jining and Linyi. The situation in 1990s was similar to that in 1980s on the whole, and the incidence rate was highest in Linyi. After 2000, the epidemic area had no change, mainly in Linyi, Rizhao and Zibo.(3) Measles the incidence rate experienced 5 stages, which were early days of usage of measles vaccine ( I stage), generalization of measles vaccine (II stage), enforcement of programming immunization (III stage), accelerated control of measles (IVstage) and elimination of measles (V stage). (1) The incidence rate in I stage was higher than that in other 4 stages. The incidence rate had obviously decreased in II stage compared with that in I stage, decreased by about 50%, but it was still higher than that in other 3 stages. The decrease of incidence rate in III stage was larger than that in II stage, the incidence rate decreased by about 96%. The incidence rate was lowest in IV stage, however, the incidence rate in V stage increased, it was about 3.4 fold of that in IV stage. (2) There was regular seasonal distribution in the incidence rate of measles, the peak of incidence rate was among the period from February to May. (3) In 43 years, measles broke out in every area in Shandong province, but there was obvious difference in the spatial distribution between different stages. In I stage, measles broke out in all areas in Shandong province, and the incidence rate was high, especially in the areas of Jining, Zaozhuang, Qingdao and Jinan. In II stage, the area of measles decreased, there was high incidence rate of measles in Heze and Linyi. In III stage, the area of measles obviously decreased, the outbreak of measles was mainly distributed in Heze, Zaozhuang and Linyi. In IV stage, the area of measles decreased further, but the outbreak was still mainly distributed in Zaozhuang and Heze. In V stage, the area of outbreak enlarged, there was highest incidence rate of measles in Binzhou, then in Dezhou, Zaozhuang, Heze, Jining and Qingdao.3. Forecast for incidence of the three main infectious diseases in Shandong province(1) HBV Based on the characteristic of the recorded HBV monthly incidence rate from 1990 to 2003, ARIMA model was applied to forecast the HBV monthly incidence rate. The best model is :X_t = Z_t - 0.6011Z_t-1-0.0645Z_t-2- 0.0803Z_t-3+0.0654Z_t-11 -0.4599Z_t-12The HBV monthly incidence rates in 2004 and 2005 were forecasted by using this model, and compared to the corresponding actual values: the average values (minimum, maximum) of the relative error in the first year and second year were respectively 13.7% (4.07%, 21.97%) and 16.9%(8.41%, 27.17%). The result showed that this model for forecast was of relatively high precision, and the effect was better to forecast in the near future than at a specified future rate. The monthly incidence rates of the 24 months in the two years of 2004 and 2005 was further added to the values from the year 1990 to 2003, and the fit final forecast model was:X_t=Z_t -0.3320Z_t-1-0.1214Z_t-2+0.0374Z_t-11 -0.4997Z_t-12This model was applied to forecast the HBV monthly incidence rate in 2006 in Shandong province, and the forecasted result showed that the HBV monthly incidence rate in 2006 in Shandong province would be between 2.87—4.70/ one hundred thousand, still with the trend to increase. This indicates that the new HBV patient would be around 35 thousand to 59 thousand in 2006 in Shandong province, and this deserves great attention from the related departments.(2) HFRS Based on the characteristic of the recorded HFRS monthly incidence rate from the year of 1990 to 2004, Wavelet analysis was applied to forecast the incidence of HFRS, and the results showed that the average (minimum, maximum) of the relative error between the forecasted value HFRS monthly incidence rate in 2005 and the actual value in this year was 8.81% (0.81%, 28.89%). The result shows that it is of higher precision to forecast the HFRS incidence rate by using Wavelet analysis. The monthly incidence rate from January to December in 2005 were added to the former data, and was analyzed by using Wavelet decomposition, to get the forecasted monthly incidence rates from January to December in 2006.The result indicated that the forecasted HFRS monthly incidence rate would decrease, and with peaks in spring, autumn and winter.(3 ) Measles According to the epidemic trend of monthly incidence rate of the Measles, to create the ARIMA model with the data from 1985-2003, the forecasting precision is low, and it is not suitable to forecast the future of the Measles, so we can use exponential smoothing methods to analysis the seasonal component and trend component. The result show that the seasonal pattern is quite stable in different periods, while the trend change with time Obviously: the incidence level grow high, and have a period change from 1963 to 1976; it decrease fast and the period disappear from 1977 to 1986; while it keep in a stable low level from 1987 to 2004. Researcher think it is difficult to forecasting the incidence rate with a mathematical model to some diseases which the incidence rate is relative low and sensitive to intervention.Conclusion:1. During 43 years from 1963 to 2005, except 1964 and 1971, the total incidence rates of 19 kinds of legal infectious diseases showed a decreasing tendency as a whole in Shandong Province, which maintained basically at a lower level after 1998. The respiratory infectious existed primarily before the 1980's, while the enteric infectious did after the 1980's. The spectrums of the first 5 infectious diseases have changed, and now they are hepatitis, hemorrhagic fever, measles, typhoid and scarlet fever.2. The incidence rate of viral hepatitis in Shandong Province was lower in the 1960's, increased in the 1970's, and decreased gradually after the 1980's. The incidence rate of hepatitis A has a decreasing tendency. It fluctuates with seasonal variation (higher in spring and autumn) and concentrates in big and middle cities (Qingdao, Jinan, Weihai and Yantai). The incidence rate of hepatitis B has an increasing tendency. It occurs in every city of entire province without the obvious seasonal fluctuation. 3. The incidence rate of hemorrhagic fever with renal syndrome (HFRS) in Shandong Province was lower in the 1960's, increased gradually from the 1970's, took a outbreak in 1986 and also in 1995, and had a stable sporadic condition after 2000. The source of infection was Apodemus in the 1970's (single spring-winter peak), a mixed type mainly with Apodemus in the 1980's (autumn-winter peak and spring peak), and a mixed type mainly with Rattus after 1990. The infectious areas concentrate in Linyi and its peripheral regions.4. The incidence rate of measles is enormously affected by immune intervention. It is highest in the earlier process of using measles vaccine. It has an approximately 50% descending rate in popularized stage, 96% in program immune, and is at a lowest level during the period of accelerating control. The incidence rate increases in eliminated stage, which is 3-4 times of the foregoing stage. The incidence of measles fluctuates with seasonal variation, occurring mostly in March, April and May. It occurs in every areas of the whole province, which is most serious in Heze and followed by Zaozhuang.5. When selecting the forecast methods, we should choose the suitable model according the time series data: (1) it can be forecasted with ARIMA model when the incidence rate of diseases (eg. hepatitis B) is higher and has a relatively stable ascending or descending tendency; (2) it is suitable to use wavelet analysis theory when the incidence rate of natural focal diseases (eg. HFRS) is higher; (3) it is difficult to forecast the incidence rate with the mathematical model regarding to the diseases (eg. measles), whose incidence rate can be decreased obviously to a lowerlever via the immune intervention.