What is the recommended treatment for disseminated shingles (varicella‑zoster infection with more than 20 lesions outside the primary dermatome or visceral involvement) in Australia?

Treatment for Disseminated Shingles in Australia

Intravenous acyclovir 10 mg/kg every 8 hours is the mandatory treatment for disseminated shingles, continuing for a minimum of 7–10 days and until all lesions have completely scabbed. 1

Definition and Recognition of Disseminated Disease

Disseminated herpes zoster is defined by:

• Skin lesions involving more than 3 dermatomes 1
• More than 20 vesicles outside the primary dermatome 2
• Evidence of visceral organ involvement (hepatitis, pneumonitis, encephalitis) 1, 3
• Presence of hemorrhagic lesions 1

The majority of disseminated cases (95%) begin as localized dermatomal disease and subsequently spread, so early recognition of progression is critical. 2

Immediate Treatment Protocol

Intravenous Acyclovir Dosing

• 10 mg/kg IV every 8 hours is the established dose for disseminated or invasive herpes zoster 1, 4
• Continue treatment for at least 7–10 days and until all lesions have completely scabbed 1
• This is the treatment of choice for all VZV infections in severely compromised hosts 1

Renal Function Monitoring

• Obtain baseline serum creatinine and creatinine clearance before initiating therapy 5
• Monitor renal function once or twice weekly during IV acyclovir therapy 1
• Dose adjustments are mandatory for any degree of renal impairment to prevent acute renal failure and drug accumulation 1
• Ensure adequate hydration throughout treatment to minimize crystalluria and acyclovir-induced nephropathy 1

Additional Monitoring

• Assess for thrombotic thrombocytopenic purpura/hemolytic uremic syndrome in immunocompromised patients receiving high-dose therapy 1
• Thrombocytopenia is detected in 56% of disseminated cases and should be monitored 2
• Perform daily assessment for new lesion formation and visceral symptoms (respiratory distress, hepatitis, neurologic changes) 3

Management of Immunosuppression

Temporarily reduce or discontinue immunosuppressive medications when clinically feasible in patients with disseminated or invasive herpes zoster. 1

• Re-introduction of immunosuppressive agents should occur only after all vesicular lesions have crusted, fever has resolved, and clinical improvement is documented on antiviral therapy 1
• Initiation or continuation of immunomodulatory therapy during active herpes zoster infection is contraindicated 1

Treatment Failure and Resistance

If lesions have not begun to resolve within 7–10 days:

• Suspect acyclovir resistance and obtain viral culture with susceptibility testing 1
• Confirmed acyclovir-resistant VZV occurs in up to 7% of immunocompromised patients 1
• For proven resistance, switch to foscarnet 40 mg/kg IV every 8 hours until clinical resolution 1
• All acyclovir-resistant strains are also resistant to valacyclovir, and most are resistant to famciclovir 1

Infection Control Measures

For disseminated zoster, implement both airborne and contact precautions in addition to standard precautions:

• Place patient in a negative-air-flow isolation room until all lesions are dry and crusted 3
• Only healthcare personnel with documented VZV immunity should provide care 3
• Patients remain contagious 1–2 days before rash onset and until all lesions are crusted 3
• Physical separation of at least 6 feet from other patients is required in healthcare settings 1

High-Risk Populations Requiring Aggressive Management

Disseminated disease is most common in:

• Immunocompromised patients (58.5% of disseminated cases) 2
• Patients on active chemotherapy, HIV infection, organ transplant recipients, chronic immunosuppression 1, 3
• Elderly immunocompetent patients (mean age 82 years), where immunosenescence plays a role 2

Approximately 30% of immunocompromised patients develop severe disease with primary VZV infection, and visceral dissemination carries significant mortality risk without prompt antiviral therapy. 3

Common Pitfalls to Avoid

• Do not use oral antivirals for disseminated disease—IV therapy is mandatory regardless of immune status 1, 6
• Do not discontinue treatment at exactly 7 days if lesions are still forming or have not completely scabbed 1
• Do not delay IV acyclovir while awaiting diagnostic confirmation in immunocompromised patients with suspected dissemination 3
• Do not apply topical antivirals—they are substantially less effective than systemic therapy 1
• Skin lesions may continue to appear for 7–14 days in immunocompromised patients (versus 4–6 days in immunocompetent hosts), requiring extended treatment duration 1, 3

Post-Recovery Vaccination

After recovery, administer the recombinant zoster vaccine (Shingrix) for all adults ≥50 years:

• Provides >90% efficacy in preventing future herpes zoster episodes 1, 5
• Two-dose series with second dose given 2–6 months after the first 5
• Recommended regardless of prior herpes zoster episodes 1