Counts of Dengue hemorrhagic fever reported in EL SALVADOR: 1987-2012

Project Tycho datasets contain case counts for reported disease conditions for countries around the world. The Project Tycho data curation team extracts these case counts from various reputable sources, typically from national or international health authorities, such as the US Centers for Disease Control or the World Health Organization. These original data sources include both open- and restricted-access sources. For restricted-access sources, the Project Tycho team has obtained permission for redistribution from data contributors. All datasets contain case count data that are identical to counts published in the original source and no counts have been modified in any way by the Project Tycho team. The Project Tycho team has pre-processed datasets by adding new variables, such as standard disease and location identifiers, that improve data interpretabilty. We also formatted the data into a standard data format.Each Project Tycho dataset contains case counts for a specific condition (e.g. measles) and for a specific country (e.g. The United States). Case counts are reported per time interval. In addition to case counts, datsets include information about these counts (attributes), such as the location, age group, subpopulation, diagnostic certainty, place of aquisition, and the source from which we extracted case counts. One dataset can include many series of case count time intervals, such as "US measles cases as reported by CDC", or "US measles cases reported by WHO", or "US measles cases that originated abroad", etc.Depending on the intended use of a dataset, we recommend a few data processing steps before analysis:- Analyze missing data: Project Tycho datasets do not inlcude time intervals for which no case count was reported (for many datasets, time series of case counts are incomplete, due to incompleteness of source documents) and users will need to add time intervals for which no count value is available. Project Tycho datasets do include time intervals for which a case count value of zero was reported.- Separate cumulative from non-cumulative time interval series. Case count time series in Project Tycho datasets can be "cumulative" or "fixed-intervals". Cumulative case count time series consist of overlapping case count intervals starting on the same date, but ending on different dates. For example, each interval in a cumulative count time series can start on January 1st, but end on January 7th, 14th, 21st, etc. It is common practice among public health agencies to report cases for cumulative time intervals. Case count series with fixed time intervals consist of mutually exxclusive time intervals that all start and end on different dates and all have identical length (day, week, month, year). Given the different nature of these two types of case count data, we indicated this with an attribute for each count value, named "PartOfCumulativeCountSeries".

Project Tycho数据集收录全球各国上报的各类疾病的病例统计数据。Project Tycho数据整理团队从各类权威数据源中提取上述病例统计数据，此类数据源通常来自各国或国际卫生主管机构，例如美国疾病控制与预防中心（US Centers for Disease Control）与世界卫生组织（World Health Organization）。上述原始数据源涵盖开放获取与受限访问两类。针对受限访问数据源，Project Tycho团队已获得数据提供方的再分发许可。所有数据集内的病例统计数据均与原始数据源发布的统计结果完全一致，Project Tycho团队未对任何统计数值进行修改。Project Tycho团队已对数据集进行预处理，新增了标准化疾病与位置标识符等变量，以提升数据的可解释性；同时将数据统一整理为标准格式。每份Project Tycho数据集仅针对特定疾病（如麻疹）与特定国家（如美国）收录病例统计数据，且统计数据按时间区间上报。除病例统计数值外，数据集还包含与统计数据相关的元信息（属性），例如数据所属地区、年龄分组、亚群体、诊断确定性、感染来源以及数据提取来源等。单个数据集可包含多组病例统计时间序列，例如"美国疾病控制与预防中心上报的美国麻疹病例数"、"世界卫生组织上报的美国麻疹病例数"，以及"境外输入型美国麻疹病例数"等。根据数据集的具体使用场景，我们建议在开展分析前完成以下数据处理步骤：- 处理缺失数据：Project Tycho数据集未包含无病例上报的时间区间（由于源文档不全，多数数据集的病例时间序列存在缺失），使用者需自行补充无统计数值的时间区间；不过Project Tycho数据集已包含病例数为0的时间区间。- 区分累计型与非累计型时间区间序列：Project Tycho数据集中的病例时间序列可分为"累计型"与"固定区间型"两类。累计型病例时间序列由重叠的时间区间构成，这类区间均始于同一日期，但终止日期各不相同。例如，某累计型计数时间序列中的每个区间均始于1月1日，终止日期则分别为1月7日、14日、21日等。公共卫生机构通常采用累计时间区间上报病例数据。固定区间型病例时间序列则由互斥的时间区间构成，所有区间的起止日期均不相同，但区间长度一致（如日、周、月、年）。鉴于两类病例数据的性质存在差异，我们为每个统计数值新增了名为"PartOfCumulativeCountSeries"的属性，用以标识其所属类型。