Mode of Collection:
State epidemiologists report cases of notifiable diseases to CDC, which tabulates these data weekly, and in annual summaries.
Data include the incidence of reportable diseases using uniform case definitions.
Notifiable disease reports are received from health departments in the 50 states, 5 territories, New York City, and the District of Columbia.
Notifiable disease surveillance is conducted by public health practitioners at local, state, and national levels to support disease prevention and control activities. The Council of State and Territorial Epidemiologists and CDC annually review the status of national infectious disease surveillance and recommend additions or deletions to the list of nationally notifiable diseases based on the need to respond to emerging priorities. Because reporting is currently mandated by law or regulation only at the local and state levels, the list of diseases that are considered notifiable varies slightly by state. State epidemiologists report cases of notifiable diseases to CDC, which tabulates and publishes these data in Morbidity and Mortality Weekly Report (MMWR) and in Summary of Notifiable Diseases, United States.
Response Rates and Sample Size:
NNDSS data must be interpreted in light of reporting practices. If persons who have a reportable disease do not seek medical care from a health care provider, the case may not 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 public health officials. Finally, factors such as changes in case definitions for 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.