What is the diagnosis and treatment for a respiratory illness followed by small vesicles on the back of the neck?

Diagnosis: Varicella-Zoster Virus (VZV) Reactivation or Enterovirus Infection

The most likely diagnosis is varicella-zoster virus (VZV) reactivation presenting as herpes zoster (shingles), though enterovirus infection should also be considered given the respiratory prodrome followed by vesicular eruption. 1

Diagnostic Approach

Immediate Vesicle Sampling

• Obtain vesicle fluid for PCR and viral culture immediately, as this provides the highest diagnostic yield for identifying the causative pathogen 1
• Vesicular swabs are most useful because they indicate acute and systemic infection, unlike throat or stool samples which may represent prolonged viral shedding 1
• PCR is more sensitive than viral culture or electron microscopy for detecting HSV and VZV 1

Respiratory Tract Sampling

• Collect throat swab or nasopharyngeal aspirate for PCR testing of respiratory viruses and enteroviruses, given the preceding respiratory illness 1
• When recent or concomitant respiratory tract infection is present, respiratory specimens should be sent for viral PCR 1
• Rectal swab for enterovirus PCR should be considered, though vesicle sampling is more diagnostically useful 1

Key Clinical Distinctions

VZV (Herpes Zoster) Features:

• Vesicles typically follow a dermatomal distribution on the neck
• Usually preceded by prodromal pain or paresthesias in the affected dermatome
• Respiratory symptoms may represent coincidental upper respiratory infection or early systemic viral symptoms

Enterovirus Features:

• Hand-foot-and-mouth disease pattern with vesicles that may appear on neck/trunk 1
• More common in children but can occur in adults
• Respiratory prodrome is characteristic of enterovirus infections 1

Treatment Recommendations

For Suspected VZV (Most Likely):

• Initiate antiviral therapy with oral acyclovir (800 mg five times daily), valacyclovir (1000 mg three times daily), or famciclovir (500 mg three times daily) for 7-10 days
• Treatment should begin within 72 hours of rash onset for maximum efficacy
• Earlier treatment reduces pain severity, duration of viral shedding, and risk of postherpetic neuralgia

For Suspected Enterovirus:

• Management is primarily supportive as no specific antiviral therapy exists for enterovirus infections
• Symptomatic treatment includes analgesics and antipyretics
• Monitor for neurological complications if symptoms progress 1

Critical Pitfalls to Avoid

Do not prescribe empiric antibiotics without clear evidence of bacterial superinfection 1, 2

• Vesicular lesions on the neck following respiratory illness are viral in etiology
• Antibiotic use without bacterial infection signs delays appropriate diagnosis and promotes resistance 1, 2
• Local signs of bacterial infection (warmth, erythema, purulent drainage, significant tenderness) must be present to justify antibiotics 1

Do not assume reactive lymphadenopathy from respiratory infection 1, 2

• While reactive cervical lymphadenopathy commonly occurs with respiratory infections, any neck mass present ≥2 weeks requires evaluation for malignancy 1, 2
• If lymphadenopathy persists beyond resolution of respiratory symptoms, further workup including imaging is indicated 1, 2

Monitoring and Follow-Up

• Reassess within 48-72 hours to confirm vesicles are crusting and no new lesions are appearing
• If vesicles do not follow expected viral course or worsen despite antiviral therapy, consider alternative diagnoses including bacterial superinfection or disseminated disease
• Watch for complications including secondary bacterial infection, disseminated zoster (especially in immunocompromised patients), or neurological involvement
• PCR results should guide definitive diagnosis and allow discontinuation of unnecessary treatments 1