How We Conduct Case Surveillance

Case surveillance begins with local, regional, state, and territorial public health agencies. The data they collect about confirmed diagnoses of certain health conditions shows how often that disease occurs in their area. Health officials can use the information to quickly identify outbreaks and control the spread of disease. It also helps researchers identify disease trends and track outbreaks.

You can think of the national case surveillance process as a data supply chain. It’s made up of two components:

  1. Case reporting, in which hospitals, healthcare providers, and laboratories report positive lab results or information on people diagnosed with a certain condition to appropriate health departments according to state disease reporting laws. Case reporting is mandatory.
  2. Case notification, in which state and local health departments send deidentified data about confirmed cases of certain diseases and conditions that are tracked nationally to CDC. Case notification is voluntary.

Case Reporting

A person feels ill and goes to the doctor.

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A doctor diagnoses and/or a laboratory confirms a reportable disease.

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The hospital, healthcare provider, or laboratory sends information about this case to the public health department.

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The public health department receives disease data and uses them to:

Identify and control disease outbreaks.

Ensure that every patient is effectively treated.

Provide testing and preventive care to those exposed.

Case Notification

The public health department sends de-identified data about national notifiable diseases to CDC.

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The NNDSS team receives, secures, processes, and provides de-identified data to disease-specific programs across CDC.

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CDC programs use disease-specific data to:

Support recognition of disease outbreaks.

Monitor shifts in disease patterns.

Evaluate and fund disease control activities.

CDC Support for Case Surveillance

CDC provides case surveillance resources and guidance to patients, healthcare teams, and public health agencies, such as:

  • health information for patients in various forms, including websites, fact sheets, toolkits, and brochures and pamphlets;
  • guidance to healthcare teams, such as clinical information, research, publications like Morbidity and Mortality Weekly Report (MMWR), Vital Signs, and Community Guide; and
  • support to public health agencies, such as guidance, data collection and reporting, large and small-scale outbreak assistance, and funding. CDC also issues alerts through the Health Alert Network (HAN) and Epidemic Information Exchange (Epi-X) Network.

Paula Yoon, ScD, MPH, director of the Division of Health Informatics and Surveillance, talks about how data from disease surveillance protect public health.

Technology, Standards, and Regulations Used for Case Surveillance

Electronic Case Reporting

Electronic case reporting (eCR) is the automated, real-time exchange of case report information between electronic health records (EHRs) and public health agencies. It moves data quickly, securely, and seamlessly from EHRs in healthcare facilities to state or local health departments. eCR enables immediate feedback from public health agencies to healthcare facilities about reportable conditions and possible outbreaks, which is especially critical during public health emergencies.

Electronic Laboratory Reporting

Electronic laboratory reporting (ELR) is the automated transmission of laboratory reports from laboratories to state and local public health departments. ELR improves the reporting of notifiable conditions, which in turn benefits public health responses to outbreaks.

Integrated Surveillance Information Systems

National Electronic Disease Surveillance System (NEDSS) is a set of architectural standards for integrated surveillance information systems in reporting jurisdictions. Systems based on these standards are primary data sources for NNDSS. Jurisdictions use these information systems to receive data on reportable conditions in eCRs from healthcare and ELRs from laboratories. They add information collected during case investigations and disease control activities. Jurisdictions also use these systems to create and send standards-based case notifications to CDC for NNDSS.

International Event Reporting

Healthcare providers in the United States are required to report diseases, conditions, and outbreaks determined to be reportable by local, state, or territorial law or regulation. In addition, all healthcare providers work with their local, state, or territorial health agencies to identify and report events occurring in their location that might constitute a Public Health Emergency of International Concern (PHEIC). A PHEIC is an extraordinary event that constitutes a public health risk to other countries through international spread of disease and potentially requires a coordinated international response. All World Health Organization (WHO) member countries are required to notify WHO of a potential PHEIC. WHO makes the final determination about the existence of a PHEIC.

In the case of human diseases, the U.S. departments of health notify CDC through existing formal and informal reporting mechanisms. CDC further analyzes the event by use of the decision algorithm in Annex 2 of the International Health Regulations (IHR) and notifies the U.S. Department of Health and Human Services (DHHS) Secretary’s Operations Center (SOC), as appropriate. When a potential PHEIC is identified, WHO member countries have 48 hours to assess the risk of the reported event. If authorities determine that a potential PHEIC exists, the WHO member country has 24 hours to report the event to WHO. The DHHS SOC is responsible for reporting a potential PHEIC to WHO.

Message Evaluation and Testing Service

The Message Evaluation and Testing Service (METS) is a message validation service for public health jurisdictions to use to evaluate HL7 case notification messages before they are sent through the Message Validation, Processing, and Provisioning System (MVPS) for processing and provisioning to CDC programs.

Message Validation, Processing, and Provisioning System

MVPS is software that receives national notifiable disease data from jurisdictions, validates and processes the data, and provisions them to CDC programs. Through the MVPS Portal, jurisdictions have the ability to view the data they have submitted and identify data quality issues.

NEDSS Base System

The NEDSS Base System (NBS) is a CDC-developed integrated information system that helps local, state, and territorial public health departments manage reportable disease data and send notifiable disease data to CDC. NBS provides a tool to support the public health investigation workflow and to process, analyze, and share disease-related health information. NBS also provides reporting jurisdictions with a NEDSS-compatible information system to transfer epidemiologic, laboratory, and clinical data efficiently and securely over the Internet.

Page last reviewed: September 29, 2021