| ObjectivesWith the great natural and social changes, some of infectious diseases have already been controlled effectively or eliminated, but some of them are still dangerous to human health. Some infectious diseases that have been controlled in the past have emerged again, and some appear. Thus, infectious diseases constitute still substantial diseases burden in our country, and their prevention and control remains a hard task.37infectious diseases which are highly high incident, widely epidemic and seriously threatening have been listed as mandatory notifiable diseases by our country. Time distribution is a basic epidemiological feature of infectious disease, which can produce some etiological clues. Incidence trends and seasonality are the two important characteristics of time distribution, which can reflect the dynamic changes of diseases and the comprehensive effects of prevention and control measures, at the same time they can also give clues to the causes of disease and provide a base for disease prevention strategies and measures. The methods of studying incidence trends and seasonality of infectious diseases in our country have some limitations, which can not reflect the two characteristics maximumly and accurately.Thus, our study aims to explore the incidence trends and seasonal characteristics of the Type-B notifiable infectious diseases in our country in the past eight years by using the decomposition methods of time-serial incidence data, in order to improve the ability of forecasting and monitoring of infectious disease, and to provide the basis of causal inference and disease prevention strategies, and to enhance the understanding of biology, ecology and transmission mechanism of the infectious diseases.Methods24kinds of Type-B notifiable infectious diseases have been included in the study,5of which are incomplete in reported years zero cases at certain months have been excluded. Firstly, the monthly cases of each disease provided by Web-based National Reporting System on Notifiable Communicable Diseases from2005to2012are collected, and adjusted by the days in each month and population growth rate. Secondarily, long-term trend (MAi), seasonality S and SR; of each disease have been split out by using decomposition methods, and curves of time-series data have been drawn. Thirdly, the incidence trends are inferred and classified via the shape of MA;, significant levels of seasonality, peak or valley periods of incidence are inferred and classified via the shape of S and SRi and cluster analysis of S. And finally, peak or valley periods of infection are inferred via the comprehensive analysis of the above results and the incubation period.ResultsIncidence trends.The trend of five diseases, Hepatitis C, syphilis, HIV, Hepatitis E and brucellosis, is rising. The trend of six diseases, gonorrhea, neonatal tetanus, epidemic cerebrospinal meningitis, Typhoid and paratyphoid fever, bacillary dysentery and intestinal amebiasis and anthrax is decreasing. The trend of five diseases, malaria, rabies, Hepatitis A, measles and Tuberculosis, is increasing firstly and then decreasing. The trend of two diseases, hemorrhagic fevers and schistosomiasis, is firstly decreasing and then increasing. The trend of three diseases, scarflet fever, pertussis, and Hepatitis B, is fluctuant. The trend of three diseases, epidemic encephalitis B, dengue fever, and leptospirosis is stair-stepping.Significant levels of seasonality.There are three diseases, epidemic encephalitis B, dengue fever and Ieptospirosis, with very significant seasonality; seven diseases, anthrax, measles, hemorrhagic fevers, epidemic cerebrospinal meningitis, bacillary dysentery and intestinal amebiasis, malaria and scarflet fever, with relatively remarkable seasonality; six diseases, brucellosis, pertussis, Hepatitis E, schistosomiasis, Typhoid and paratyphoid fever and rabies, with minor remarkable seasonality; and eight diseases, HIV, neonatal tetanus, Tuberculosis, Hepatitis A, Hepatitis B, Hepatitis C, syphilis and gonorrhea, with unremarkable seasonality.Incidence cycle.13diseases, epidemic encephalitis B, dengue fever, leptospirosis, anthrax, epidemic cerebrospinal meningitis, bacillary dysentery and intestinal amebiasis, malaria, brucellosis, pertussis, Hepatitis E, schistosomiasis, Typhoid and paratyphoid fever and rabies, are uni-peak-type. Three diseases, leptospirosis, hemorrhagic fevers and scarflet fever, are two-peak-type. Eight diseases, HIV, neonatal tetanus, Tuberculosis, Hepatitis A, Hepatitis B, Hepatitis C, syphilis and gonorrhea, are pluri-peak-type or non-peak-type.Peak periods of infection.The infection of two respiratory infectious disease, measles and epidemic cerebrospinal meningitis, two zoonosis-borne diseases, hemorrhagic fevers and brucellosis, and one gastrointestinal infectious diseases, Hepatitis E, are highest in spring. The infection of two respiratory infectious disease, pertussis and scarflet fever, two gastrointestinal infectious diseases, bacillary dysentery and intestinal amebiasis and Typhoid and paratyphoid fever, and all the zoonosis-borne diseases are highest in summer. The infection of two zoonosis-borne diseases, dengue fever, hemorrhagic fevers and leptospirosis, are highest in autumn. The infection of two respiratory infectious disease, epidemic cerebrospinal meningitis and scarflet fever, and one gastrointestinal infectious diseases, Hepatitis E, are highest in winter.ConclusionsThe incidence trends of most of the infectious diseases continue to rise or fluctuate, which implies that prevention and control of infectious diseases remains a hard task, especially for those five disease which have been keeping on the rise.The trends of most respiratory and gastrointestinal infectious diseases are decreasing, while those of most blood or sexually transmitted diseases are on the rise. It could be imply that prevention and control strategies are more effective for the former than the latter in recent years. In the future, more efforts should be pursued to the control of blood and sexually transmitted diseases.Seasonality of vector-borne or natural focal diseases are significant, but those of respiratory and gastrointestinal infectious diseases are relatively remarkable, and those of blood and sexually transmitted diseases are unremarkable.Most infectious diseases are uni-peak-type, while scarflet fever, hemorrhagic fevers and leptospirosis, are two-peak-type, which needs special attention to explore causes and carry out related prevent and control tasks before two peaks.Infections of respiratory infectious diseases and Hepatitis E are most commonly seen in autumn and winter, while vector-borne or natural focal diseases and gastrointestinal infectious diseases are in summer and autumn. Peak periods of infection will be of more significance than that of incidence, because it benefits the research of prevention and mechanisms of relative diseases.Advantages of this paper are as follows. Data comes from Web-based National Reporting System on Notifiable Communicable Diseases began in2004, and data has been collected since2005in case of the incompleteness parts in the first year. Numers of incidence have been adjusted by the days in each month and population growth rate in order to remove bias. Then the trends and seasonality have been split out by using decomposition methods to remove the interferenceof some unrelated factors. And date are used to the maximum. Trends and seasonality are visually discerned via the curves. Comparison of significant levels of seasonality can be performed by the value of S.Disadvantages of this paper are as follows. Decomposition methods are lack of statistical indicators to demonstrate their statistically significance. Judgment of significant levels of seasonality and peak periods is subjective.In this paper, the basic monthly data is the sum of incidence cases from the whole country. Since China has a vast territory, natural and social factors that affect the incidence of infectious diseases in different regions are possibly distinct. Thus, by using the same methods in this study, data from a smaller geographic area should be analyzed in the future. |
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