The similar presentation and timing of these 2 VZV cases caused concern for an unidentified community outbreak. The infection control team was notified; additionally, per hospital protocol the state health department was alerted as well as the clinicians and staff of the hospital with a request to be vigilant for further cases.
Despite high vaccination rates in the United States, outbreaks of varicella still occur, particularly among unvaccinated individuals, and a robust and efficient response is necessary to control the spread of such outbreaks.4 Many states, including Arkansas where our cases occurred, have laws mandating report of VZV cases to the department of health.5 Dermatologists play an important role in reporting cases, aiding in diagnosis through recognition of the physical examination findings, obtaining appropriate biopsy, and recommending additional laboratory testing.
Typical skin manifestations include a pruritic rash of macules, papules, vesicles, and crusted lesions distributed throughout the trunk, face, arms, and legs. Because new lesions appear over several days, they will be in different stages of healing, resulting in the simultaneous presence of papules, vesicles, and crusted lesions.6 This unique characteristic helps distinguish VZV from other skin diseases such as smallpox or mpox (monkeypox), which generally show lesions in similar stages of evolution.
Biopsy also can aid in identification. Viruses in the herpes family reveal similar histopathologic characteristics, including acantholysis and vesicle formation, intranuclear inclusions with margination of chromatin, multinucleation, and nuclear molding.7 Immunohistochemistry can be used to differentiate VZV from herpes simplex virus; however, neither microscopic examination nor immunohistochemistry distinguish primary VZV infection from herpes zoster (HZ).8
The mpox rash progresses more slowly than a VZV rash and has a centrifugal rather than central distribution that can involve the palms and soles. Lymphadenopathy is a characteristic finding in mpox.9 Rickettsialpox is distinguished from VZV primarily by the appearance of brown or black eschar after the original papulovesicular lesions dry out.10 Atypical hand, foot, and mouth disease can manifest in adults as widespread papulovesicular lesions. This form is associated with coxsackievirus A6 and may require direct fluorescent antibody assay or polymerase chain reaction of keratinocytes to rule out VZV.11
Herpes zoster occurs in older adults with a history of primary VZV.6 It manifests as vesicular lesions confined to 1 or 2 adjacent dermatomes vs the diffuse spread of VZV over the entire body. However, HZ can become disseminated in immunocompromised individuals, making it difficult to clinically distinguish from VZV.6 Serology can be helpful, as high IgM titers indicate an acute primary VZV infection. Subsequently increased IgG titers steadily wane over time and spike during reactivation.12
Dermatology and infectious disease consultations in our cases yielded a preliminary diagnosis through physical examination that was confirmed by biopsy and subsequent laboratory testing, which allowed for a swift response by the infection control team including isolation precautions to control a potential outbreak. Patients with VZV should remain in respiratory isolation until all lesions have crusted over.6