Is herpes zoster (shingles) infectious to susceptible individuals?

Is Herpes Zoster Infectious?

Yes, herpes zoster (shingles) is infectious and can transmit varicella-zoster virus to susceptible individuals who have not had chickenpox or the varicella vaccine, potentially causing chickenpox in these individuals—though it is significantly less contagious than chickenpox itself, with approximately 20% of the transmission risk. 1

Transmission Mechanism and Risk Profile

Herpes zoster transmits VZV through direct contact with fluid from active vesicles or, rarely in healthcare settings, through airborne exposure to viral particles from uncrusted lesions. 1 The virus enters susceptible hosts through the upper respiratory tract or conjunctiva. 2

Key transmission characteristics include:

• Household transmission risk is approximately 20% of the risk seen with chickenpox, making shingles substantially less contagious than primary varicella infection 1
• Airborne transmission is possible but primarily documented in healthcare settings where susceptible persons with no direct contact with the index patient have acquired infection 1
• A person with shingles cannot give another person shingles directly—they can only transmit VZV, which causes chickenpox in susceptible individuals 1
• Shingles itself occurs only as reactivation of latent virus in someone who previously had chickenpox or the vaccine 1

Contagious Period

The period of contagiousness begins 1-2 days before rash onset and continues until all lesions have dried and crusted, typically 4-7 days after rash onset. 1 For non-crusting lesions (macules and papules), contagiousness ends when no new lesions appear within a 24-hour period. 1

Antiviral therapy reduces time to lesion healing but does not immediately render the patient non-contagious—viral shedding continues until lesions are fully crusted. 1 This is a critical pitfall to avoid in clinical practice.

High-Risk Populations Requiring Protection

Individuals with active shingles should avoid contact with: 1

• Pregnant women (particularly concerning if exposure occurs 5 days before to 2 days after delivery, with newborns facing 17-30% risk of severe infection) 1
• Premature infants and neonates 1
• Immunocompromised persons of all ages 1
• Anyone without history of chickenpox or varicella vaccination 1

Special Considerations for Immunocompromised Patients

Immunocompromised patients experience markedly extended contagious phases, with new lesions continuing to appear for 7-14 days or longer (compared with 4-6 days in healthy individuals), and lesion healing is slower. 1 These patients may experience prolonged viral shedding and require longer periods of isolation. 1

Without prompt antiviral therapy in immunocompromised individuals, the risk of disseminated varicella-zoster infection rises to 10-20%. 1

Infection Control Precautions

For Immunocompetent Patients with Localized Herpes Zoster:

• Standard and contact precautions are sufficient 1
• Maintain at least 6 feet physical separation from other patients 1
• Patient should wear a surgical mask to prevent droplet transmission 1
• Complete lesion coverage is mandatory 1
• Airborne precautions are not required 1
• Continue precautions until all lesions are dried and crusted 1

For Disseminated Herpes Zoster or Immunocompromised Patients:

• Airborne and contact precautions are mandatory, regardless of immune status 1
• Negative air-flow room required 1
• Continue precautions until all lesions are dry and crusted 1
• Immunocompromised patients with any herpes zoster require airborne and contact precautions until disseminated infection is ruled out 1

Healthcare Worker Restrictions

Healthcare workers with localized herpes zoster who are immunocompetent should cover all lesions completely and be restricted from caring for high-risk patients until all lesions have dried and crusted. 1 Healthcare workers with disseminated zoster or localized zoster in immunocompromised individuals must be excluded from duty until all lesions have dried and crusted. 1

For non-crusting lesions, complete work clearance without restrictions is permitted when no new lesions appear within 24 hours. 1

Practical Prevention Measures

Patients with active shingles should: 1

• Wash hands frequently with soap and water
• Use separate towels and pillows from household members
• Keep all lesions covered when around others
• Avoid close physical contact with high-risk individuals until all lesions are crusted

Common Pitfalls to Avoid

• Assuming antiviral therapy immediately makes the patient non-contagious—viral shedding continues until lesions are fully crusted 1
• Allowing healthcare workers with herpes zoster to care for high-risk patients before lesions are fully crusted 1
• Inadequate covering of lesions, which can lead to transmission even with localized disease 1
• Failing to recognize that immunocompromised patients may have prolonged periods of viral shedding and contagiousness 1