Communicable Disease Reporting Rule Update: Reporting All Cases of Varicella

Beginning January 1, 2013, the Minnesota Department of Health (MDH) will require reporting of all cases of varicella (chickenpox).

On this page:
On what basis has the rule been update for varicella
Why is case-based reporting of varicella important

What varicella cases should be reported

What is the clinical presentation of varicella
How should cases be reported

What information should be reported
Why can't providers rely on laboratories to report varicella cases
What laboratory testing is recommended for varicella
What specimens should be collected for varicella PCR or viral culture

PDF version for print:
Communicable Disease Reporting Rule Update: Reporting All Cases of Varicella (PDF: 33KB/2 pages)

On what basis has the Communicable Disease Reporting Rule been updated for varicella?

In 2005, MDH revised the Communicable Disease Reporting Rules (Minn. Rules Chapter 4605). At that time, only unusual case incidence, critical illness, and laboratory-confirmed cases of varicella were reportable. In addition, MDH was given the authority to conduct sentinel surveillance to assess the changing epidemiology of varicella and vaccine effectiveness. The Rules also allowed the Commissioner of Health to require case-based varicella reporting if the commissioner determines that “sentinel surveillance can no longer provide adequate data for epidemiologic purposes.” (Minn. Rule. 4605.7042)

In August 2012, the Commissioner of Health determined that declining varicella incidence necessitates universal case-based reporting. During the 2011-12 school year, the 80 sentinel school sites reported only 35 cases. Also, a majority of states currently require case-based varicella reporting.

Why is case-based reporting of varicella important?

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

What 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, and differentiate phone diagnosed cases from those that are seen by a provider and/or are laboratory confirmed. Laboratory-confirmed and clinically diagnosed varicella cases - including those diagnosed by phone - will be entered into the Minnesota Immunization Information Connection (MIIC) by MDH staff, unless the provider requests to have the case excluded from MIIC. This documentation may subsequently be used as evidence of immunity to varicella.

What is the clinical presentation of varicella?

The CDC case definition for varicella is: an illness with acute onset of diffuse (generalized) maculopapulovesicular rash without other apparent cause.

Vaccinated ("breakthrough") cases may have a milder and atypical clinical presentation, with macule and papules but few or no vesicles.

How should cases be reported?

Cases may be reported through any of the mechanisms currently available for reporting communicable diseases, including the following:

Varicella cases should be reported within one working day (Monday through Friday) so that public health interventions may be implemented in a timely manner.

What information should be reported?

Information reported should include the basic information included on the Communicable Disease Reporting Card ("Yellow Card"). Cases should be reported specifically as varicella (rather than as varicella-zoster). In addition, providers should report varicella vaccination and/or disease history. MDH may contact providers for additional information. MDH may also interview cases or parents/guardians to obtain additional information including disease severity, as well as to identify and respond to any public health concerns.

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

Provider reporting is needed for the following reasons:

  • Laboratory testing does not distinguish varicella (chickenpox) from zoster (shingles).
  • False negative results may occur, especially in mild cases of breakthrough disease (in fully- or partially-vaccinated cases).
  • Currently, laboratory testing is not performed on most varicella cases. It is important to report cases that are not laboratory-confirmed to determine the true incidence of varicella.

What laboratory testing is recommended for varicella?

  • PCR (polymerase chain reaction) is the most reliable method of laboratory testing for varicella zoster virus (VZV).
  • Viral culture for VZV and detection of VZV DNA by direct fluorescent antibody (DFA) are also acceptable for confirmation of disease.
  • Serologic testing is not recommended for diagnosis because of problems with sensitivity and specificity.

What specimens should be collected for varicella PCR or viral culture?

Lesion crusts and fluid from vesicles provide the highest yield. Specimens from macules and papules can be obtained by rubbing the lesion(s) with the edge of a glass slide.

Updated Tuesday, 12-Feb-2013 16:25:10 CST