Why You Report All Cases of Varicella

All cases of varicella (chickenpox) are required to be reported to the Minnesota Department of Health (MDH).

On this page:
Why is case-based reporting of varicella important?
What varicella cases should be reported?
What is the clinical presentation of varicella?
Will reported varicella cases be entered into MIIC?
How should cases be reported
Why can't providers rely on laboratories to report varicella cases?

Why is case-based reporting of varicella important?

Case-based reporting of varicella provides the data needed to assess the changing epidemiology of varicella and evaluate the effectiveness of current immunization strategies. It also provides greater opportunity to implement exposure follow-up for high-risk contacts and outbreak control measures.

Which varicella cases should be reported?

• Clinically diagnosed cases (without laboratory confirmation) seen by a provider in a health care setting,
• Clinically diagnosed cases based on symptoms relayed by phone to the provider by the patient or parent/guardian, and
• Laboratory-confirmed cases.

It is important to report all of the above cases so that MDH can adequately assess the incidence of varicella. Cases not seen by a provider but diagnosed by phone are thought to currently represent a large proportion of total cases. MDH will collect data on how the case was diagnosed, as well as differentiate phone diagnosed cases from those that are seen by a provider and/or are laboratory confirmed.

Please note that a rash description is required for all clinically diagnosed cases, especially if laboratory confirmation is not possible or available.

What is the clinical presentation of varicella?

The CDC case definition for varicella:
In the absence of a more likely alternative diagnosis,

• An acute illness with a generalized rash with vesicles (maculopapulovesicular rash), OR
• An acute illness with a generalized rash without vesicles (maculopapular rash).

This definition was updated January 1, 2024.

Will reported varicella cases be entered into MIIC?

Cases that meet the clinical case definition and are confirmed by laboratory testing will be entered into the Minnesota Immunization Information Connection (MIIC) by MDH staff. This documentation may subsequently be used as evidence of immunity to varicella.

How should cases be reported?

Varicella cases should be reported within one business day so that public health interventions may be implemented in a timely manner. To report a case visit Reporting Varicella (Chickenpox).

Why can't providers rely on laboratories to report varicella cases?

Provider reporting is needed because:

• Laboratory testing does not distinguish varicella (chickenpox) from zoster (shingles).
• Laboratory confirmation may not always be available and false negative results can occur.
• There can be a delay in receipt of laboratory results.
• It is important to report cases that are not laboratory-confirmed to determine the true incidence of varicella.