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National Notifiable Diseases Surveillance System (NNDSS)

Centers for Disease Control and Prevention (CDC)

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Overview

NNDSS is a nationwide collaboration that enables all levels of public health (local, state, territorial, federal, and international) to share health information to monitor, control, and prevent the occurrence and spread of state-reportable and nationally notifiable infectious and some noninfectious diseases and conditions. NNDSS is a multifaceted program that includes the surveillance system for collection, analysis, and sharing of health data, resources, and information about policies and standards, at the local, state, and national levels. NNDSS provides weekly provisional and annual finalized information on the occurrence of diseases defined as notifiable by the Council of State and Territorial Epidemiologists (CSTE). Data include the incidence of nationally notifiable reportable diseases, which are reported using uniform surveillance case definitions.

Coverage

Notifiable disease reports are received from health departments in the 50 states, New York City, the District of Columbia, and 5 U.S. territories (Guam, Marshall Islands, Northern Mariana Islands, Puerto Rico, and U.S. Virgin Islands). Policies for reporting notifiable disease cases can vary by disease or reporting jurisdiction and may also vary based on case status classifications reported to CDC (that is, confirmed, probable, or suspect).

Methodology

CDC, in partnership with CSTE, administers NNDSS. Reportable disease surveillance is conducted by public health practitioners at local, state, and national levels to support disease prevention and control. Data on a subset of reportable conditions that have been designated nationally notifiable are then submitted to CDC. CDC compiles annual summaries of the finalized data. CSTE and CDC annually review the status of national notifiable disease surveillance and recommend additions or deletions to the list of nationally notifiable diseases, based on the need to respond to emerging priorities. For example, Candida auris clinical infection became nationally notifiable in 2019, and novel coronavirus disease 2019 or COVID-19 became nationally notifiable in April 2020. However, reporting nationally notifiable diseases to CDC is voluntary. Because reporting is currently mandated by law or regulation only at the local and state levels, the list of diseases that are considered reportable varies by state. For example, reporting of coccidioidomycosis to CDC is not done by some states where this disease is not reportable to local or state authorities.

State health departments report cases of nationally notifiable diseases to CDC, which tabulates and publishes these data in Morbidity and Mortality Weekly Reports (MMWR) and in Summary of Notifiable Diseases, United States (titled Annual Summary before 1985). Beginning in 2016, national notifiable disease data are released via the NNDSS website, available from: https://www.cdc.gov/nndss/index.html.

Issues Affecting Interpretation

NNDSS data must be interpreted in light of reporting practices. Some diseases that cause severe clinical illness (for example, meningococcal disease, plague, and rabies) are likely reported accurately if diagnosed by a clinician. However, people who have diseases that are clinically mild and infrequently associated with serious consequences (for example, salmonellosis) may not seek medical care from a health care provider. Even if these less severe diseases are diagnosed, they are less likely to be reported.

The degree of completeness of data reporting is also influenced by the diagnostic facilities available, the control measures in effect, public awareness of a specific disease, and the interests, resources, and priorities of state and local officials responsible for disease control and public health surveillance. Finally, factors such as changes in case definitions for public health surveillance, introduction of new diagnostic tests, or discovery of new disease entities can cause changes in disease reporting that are independent of the true incidence of disease.

In 2019, the reporting of nationally notifiable diseases may have been affected by the COVID-19 pandemic. Data from 24 jurisdictions may be incomplete: Alaska, California, Connecticut, Delaware, District of Columbia, Florida, Idaho, Indiana, Kansas, Massachusetts, Minnesota, Missouri, Montana, Nebraska, New Hampshire, New York (excluding New York City), New York City, North Dakota, Ohio, Oklahoma, South Carolina, Tennessee, Texas, and West Virginia. In addition, data from the U.S. territories of American Samoa and the U.S. Virgin Islands may also be incomplete due to the COVID-19 pandemic.

References

 

For more information, see the NNDSS website at: https://www.cdc.gov/nndss/index.html.