Counts of Intestinal infection caused by Escherichia coli O157:H7 reported in UNITED STATES OF AMERICA: 1995-2005

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".

第谷计划（Project Tycho）数据集收录了全球各国上报的各类疾病病例数统计数据。第谷计划数据整理团队从各类权威数据源提取此类病例数，数据源通常来自国家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）。这些原始数据源涵盖开放获取与受限访问两类资源。针对受限访问数据源，第谷计划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数统计均与原始数据源发布的数值完全一致，第谷计划团队未对任何病例数进行修改。
第谷计划团队已对数据集完成预处理：新增标准化疾病与位置标识符等变量，以提升数据可解释性；同时将数据统一整理为标准数据格式。每份第谷计划数据集仅针对特定疾病（如麻疹）与特定国家（如美国）收录病例数，病例数按时间区间进行上报统计。
除病例数外，数据集还包含该统计数据的相关属性信息，例如统计地点、年龄分组、亚群、诊断确定性、感染来源以及病例数提取的原始数据源。单份数据集可包含多组病例数时间序列，例如"美国疾控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"境外输入性美国麻疹病例数"等。
根据数据集的使用场景，我们建议在分析前完成以下数据处理步骤：
- 处理缺失数据：第谷计划数据集未收录无病例数上报的时间区间（由于原始文档不全，多数数据集的病例数时间序列存在缺失），使用者需自行补充无统计数值的时间区间；而数据集已收录病例数为0的时间区间。
- 区分累计与非累计时间区间序列：第谷计划数据集内的病例数时间序列可分为"累计型"与"固定区间型"两类。累计型病例数时间序列由起始日期相同、终止日期不同的重叠区间组成，例如某累计计数序列的所有区间均始于1月1日，终止日分别为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。固定区间型病例数序列则由互不重叠的时间区间构成，所有区间的起止日期均不相同，但时长完全一致（如日度、周度、月度或年度）。鉴于两类病例数数据的本质差异，我们为每个统计值新增了名为"PartOfCumulativeCountSeries"的属性，以标注其所属序列类型。