Chickenpox Reporting and Surveillance

At a glance

Learn why varicella (chickenpox) surveillance data are needed, the definitions for varicella clinical cases, how to classify cases as probable or confirmed, and how to report varicella deaths.

Stethoscope and binder on a table in the hospital room.

Why surveillance data are needed

  • Document and monitor the impact of the varicella vaccination program on varicella morbidity and mortality.
  • Describe clinical and epidemiological characteristics of varicella cases during the varicella vaccination program.
  • Evaluate the effectiveness of chickenpox prevention strategies.
  • Evaluate chickenpox vaccine effectiveness under conditions of routine use.

Varicella case reporting

In 2002, the Council of State and Territorial Epidemiologists (CSTE) recommended that states establish case-based surveillance for varicella by 2005. All states were encouraged to conduct ongoing varicella surveillance to monitor vaccine impact on morbidity. States are encouraged to report varicella cases to the National Notifiable Diseases Surveillance System (NNDSS) via the National Electronic Disease Surveillance System (NEDSS).

As of 2020, 39 states have been conducting case-based varicella surveillance. For state-specific reporting requirements, contact the state health department.

State reportable conditions‎

The State Reportable Conditions Assessment (SRCA) is a web-based assessment of reporting requirements for conditions that must be reported by clinicians, laboratories, hospitals, and others to public health according to jurisdictional laws.

Varicella case definitions

The following varicella case definitions were approved by CSTE in June 1999. These case definitions for varicella cases and deaths can also be found on the NNDSS website.

Clinical case definition

An illness with acute onset of diffuse (generalized) maculopapulovesicular rash without other apparent cause. In vaccinated people who develop varicella more than 42 days after vaccination (called breakthrough disease), the disease is usually mild with fewer than 50 skin lesions and shorter duration of illness. The rash may also be atypical in appearance (maculopapular with few or no vesicles).

Case classification

Probable: A case that meets the clinical case definition but is not laboratory confirmed nor epidemiologically linked to another probable or confirmed case.

Confirmed: A case that meets the clinical case definition and is laboratory confirmed or is epidemiologically linked to a confirmed or a probable case.


Two probable cases that are epidemiologically linked are considered confirmed, even in the absence of laboratory confirmation.

Varicella deaths

In 1998, CSTE recommended that varicella-related deaths be placed under national surveillance. As of January 1, 1999, varicella-related deaths became nationally notifiable to CDC.

Varicella deaths can be identified through death certificates, which may be available through state vital records systems. In states using electronic records, certificates may be more readily available soon after a person dies. State health departments may also request that local health departments, providers, and hospitals report varicella deaths that occur in their community.

Varicella death investigation worksheet‎

Since varicella is vaccine preventable, all deaths due to varicella should be investigated. Investigations may provide insight into risk factors for varicella mortality and may help identify missed opportunities for and barriers to vaccination.

Where to report deaths

Deaths should be reported both to the Division of Viral Diseases at CDC ( and to NNDSS via NEDSS.