Enhanced Surveillance and Case Reporting

Federal and state public health authorities will use the information gathered through enhanced surveillance and case reporting to monitor the success of control efforts. Enhanced surveillance plans should include how to:

  • Ensure rapid identification and reporting of additional cases after an initial case is confirmed (within jurisdiction or elsewhere).
  • Conduct epidemiological analysis to estimate the population at risk, identify unexpected epidemiological features of the outbreak, and evaluate the characteristics and extent of the outbreak to develop the most effective containment and communication strategies.
  • Increase laboratory testing capabilities to quickly diagnose cases of smallpox and differentiate suspected cases from other illnesses and adverse reactions to the vaccine.
  • Monitor and report serious adverse events to vaccination.

Case Definition

The clinical case definition of smallpox is an illness with acute onset of fever ≥101°F (38.3°C) followed by a rash characterized by firm, deep-seated vesicles or pustules in the same stage of development in the same area of the body without other apparent cause. See Evaluating Patients for Smallpox: Acute, Generalized Vesicular or Pustular Rash Illness Protocol. If consultation among medical providers, state and local public health departments, and CDC determines a patient is at high risk of having smallpox, Laboratory Response Network (LRN) laboratories will conduct diagnostic testing for variola virus. CDC will conduct concurrent, confirmatory testing. Variola virus is a select agent and is subject to 42 Code of Federal Regulations Part 73.

Once an outbreak has been confirmed, classify cases as confirmed, probable, and suspect using the following definitions:

  • Confirmed case: A case of smallpox that is laboratory confirmed, or a case that meets the clinical case definition that is epidemiologically linked to a laboratory confirmed case.
  • Probable case: A case that meets the clinical case definition, or a case that does not meet the clinical case definition but is clinically consistent with smallpox and has an epidemiological link to a confirmed case of smallpox. Examples of clinical presentations of smallpox that would not meet the ordinary type (pre-event) clinical case definition are: a) hemorrhagic type, b) flat type, and c) variola sine eruptione.
  • Suspect case: A case with a febrile rash illness, with fever preceding development of rash by 1 to 4 days.

Case Reporting

Local public health departments with jurisdiction over an area with confirmed smallpox cases will need to report information about cases to their state public health departments. Public health authorities will use this information to make informed decisions about the best course of action to stop the outbreak.

The extent of the outbreak and the resources available will affect the level of investigation and reporting of smallpox cases. At minimum, public health departments should submit aggregate reports of cases and deaths by age group. 

Prepare for effective surveillance by:

  • Educating medical and public health workers on the case definitions and case classifications for smallpox and chickenpox (varicella), the disease most often confused for smallpox.
  • Establishing capability to do rapid diagnostic tests for varicella zoster virus infections (both varicella and disseminated herpes zoster).
  • Developing information management systems to monitor calls and reports received.
  • Building capability for enhanced rash illness surveillance.
  • Designating case reporting mechanisms.
  • Designating a centralized location for reporting suspect smallpox cases with 24/7 capability.
  • Identifying and testing after hours and emergency notification systems and ensuring that on-call staff has appropriate access to communication resources, such as cell phones and laptops.
  • Developing data management and reporting procedures for cases of disease and for serious adverse events from vaccination.