Our Work

For Public Health

At a glance

CDC analyzes public health data to advance research and increase understanding of neurological conditions across the United States. NNCSS offers information that can improve the lives of Americans affected by neurological conditions.

A heartwarming moment between grandfather and grandson laughing and playing on a cozy sofa indoors

Key Concepts

What is prevalence?

Prevalence tells us how many people in a specific group are living with a disease during a specified time. It's usually shown as a rate per 100,000 people.

What is a surveillance case definition?

A surveillance case definition is a set of uniform criteria used to define a disease for public health surveillance. Surveillance case definitions enable public health officials to classify and count cases consistently across the country. They are not intended to be used by healthcare providers for making a clinical diagnosis or determining how to meet an individual patient's health needs.1

Our approach to surveillance

To study the burden of neurological conditions and estimate their prevalence, CDC follows a step-by-step process:

  • Assess data sources: CDC reviews many data sources and selects the best fit for population surveillance. All personal information is removed to protect patient privacy before NNCSS receives the data.
  • Define the condition: CDC develops a specific definition that classifies patient cases based on the types of information available in the data. This definition is known as a "surveillance case definition."
  • Apply the definition: CDC applies the surveillance case definition to the data to estimate how many people have the condition.

CDC reviewed more than 30 data sources, including:

  • Claims
  • Hospital records
  • Surveys
  • Vital records
  • Electronic health records

CDC evaluates data sources' performance on important aspects of surveillance systems such as representativeness, timeliness, and data quality.2 CDC selects the data sources that provide the best fit.

External peer review

CDC asked outside experts to review NNCSS's initial methods and findings on Parkinson's disease. CDC conducted this review to meet Congressional and Office of Management and Budget requirements, based on a determination that the work could substantially impact public policy or the private sector.

External peer review prior to publication demonstrates transparency and supports scientific accuracy and reliability. The Parkinson's disease Peer Review Plan summarizes the peer reviewers' comments and CDC's responses.

Partner engagement

To develop NNCSS, CDC worked with clinical and scientific experts, national health organizations, and government agencies. CDC provides progress updates and exchanges information and expertise with NNCSS's partners to inform research and patient care.

Print
Content Source:
Office of Public Health Data, Surveillance, and Technology (OPHDST)
  1. Surveillance case definitions for current and historical conditions. National Notifiable Diseases Surveillance System (NNDSS). Updated April 12, 2024. Accessed May 5, 2025. https://ndc.services.cdc.gov/.
  2. Groseclose SL, Buckeridge DL. Public Health Surveillance Systems: Recent Advances in Their Use and Evaluation. Annu Rev Public Health. Mar 20 2017;38:57-79