Diagnostic Approach for Suspected Varicella in a College Student
Clinical diagnosis is appropriate for this presentation of varicella (chickenpox), and laboratory confirmation is not routinely necessary in immunocompetent patients with typical findings. 1
Clinical Diagnosis
The clinical presentation is highly characteristic of varicella and diagnosis can be made based on:
- Generalized vesicular rash distributed across the trunk without dermatomal pattern, distinguishing it from herpes zoster which presents unilaterally in a dermatomal distribution 1
- Prodromal symptoms of feeling unwell for 2 days before rash onset, consistent with the typical varicella presentation of fever and malaise preceding the vesicular eruption 1, 2
- Fever of 38.5°C accompanying the rash, which is expected in primary VZV infection 1, 2
- Outbreak context with similar illness in roommates, indicating the highly contagious nature of varicella with secondary attack rates reaching 90% among susceptible contacts 1
- Age and setting of an 18-year-old in a college dormitory, where unvaccinated or incompletely vaccinated young adults remain susceptible to primary VZV infection 1
When Laboratory Confirmation Is Indicated
Laboratory testing should be reserved for specific situations and is not required for this typical presentation:
- Atypical presentations where the clinical picture is unclear or diagnosis is uncertain 3, 4
- Immunocompromised patients where confirmation guides treatment intensity and duration 1, 3
- Absence of characteristic features such as lack of fever or unusual rash morphology 3
- Public health surveillance or outbreak investigation requiring definitive confirmation 1
Available Diagnostic Methods (If Needed)
If laboratory confirmation were pursued, the following tests are available in order of clinical utility:
- PCR testing of vesicular fluid or scab scraping provides the most sensitive and specific confirmation of VZV infection 1, 5
- Direct fluorescent antibody (DFA) assay on vesicular fluid offers rapid results with good sensitivity 1
- Tzanck smear showing multinucleated giant cells is an inexpensive bedside test but cannot differentiate VZV from herpes simplex virus 1, 6
- Viral culture is the traditional gold standard but is slow (5-10 days) and less sensitive than molecular methods 6, 5
- Serology (acute and convalescent IgG titers) has limited utility in acute diagnosis but can confirm recent infection retrospectively 1
Critical Management Points
Beyond diagnosis, immediate actions include:
- Initiate antiviral therapy with acyclovir 800 mg five times daily for 7-10 days if the patient is seen within 24 hours of rash onset, as adults are at higher risk for complications 1, 7
- Implement airborne and contact precautions as VZV is transmitted by direct contact, inhalation of aerosols from vesicular fluid, and infected respiratory secretions 1
- Isolate the patient from susceptible individuals until all lesions are crusted, typically 4-7 days after rash onset 1
- Identify and manage exposed contacts by determining vaccination status and offering postexposure prophylaxis with varicella vaccine within 3-5 days or VZIG within 96 hours for high-risk susceptible individuals 1
Common Pitfall to Avoid
Do not confuse this presentation with herpes zoster (shingles), which presents with unilateral dermatomal distribution rather than generalized trunk involvement, and typically occurs in older adults or immunocompromised patients due to VZV reactivation rather than primary infection 1, 3, 8