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NNDSS Data and Statistics

Before using NNDSS data, the user must determine whether provisional or finalized data best meet their needs. This page highlights the differences between these two data sets to assist the user in making that decision. Links are included in the “Provisional Data” and “Finalized Data” tabs on this site to direct readers to locations where these data are presented. The “Interpreting Data” section to the right presents information to aid readers in the interpretation of NNDSS data. The blue navigation box on the left side of this page, helps readers to review the list of nationally notifiable conditions by year, all national surveillance case definitions published since 1990, the history of notifiable condition/disease surveillance, and data elements included in NNDSS case notifications.

Provisional data are initially collected locally as a result of state, territorial, and local legislation and regulations that require health care providers, medical laboratories, and other entities to submit data on reportable conditions to state and local public health departments. The reportable conditions vary depending upon each jurisdiction’s health priorities. The reporting jurisdictions voluntarily submit case notifications for the nationally notifiable conditions to CDC. NNDSS data are considered provisional and subject to change each week until the data are reconciled and verified with the state and territorial data providers to be the final official incidence counts for a given notifiable condition and year. Cumulative counts of cases presented each week can increase or decrease as additional information becomes available and counts are updated. In any given year, for most conditions, cumulative provisional case counts and rates do not match finalized case counts and rates.

Notifiable Infectious Diseases and Conditions

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