How is herpes zoster (shingles) transmitted?

Herpes Zoster Transmission

Herpes zoster (shingles) is transmitted through direct contact with fluid from active vesicles or, rarely in healthcare settings, through airborne exposure to viral particles from uncrusted lesions—it is significantly less contagious than chickenpox (approximately 20% as transmissible) and cannot be spread through casual contact. 1

Key Transmission Mechanisms

Direct Contact Transmission

• The primary route of transmission is direct contact with vesicular fluid from active shingles lesions, which contains high concentrations of infectious varicella-zoster virus (VZV) particles. 1
• Once lesions become fully crusted, the fluid disappears and viral shedding essentially stops, rendering the patient non-infectious. 1
• Transmission requires physical contact with the fluid from vesicles—the virus cannot spread through casual contact like handshakes or being in the same room. 1

Airborne Transmission (Limited)

• Airborne transmission is possible but primarily documented in healthcare settings, particularly in hospitals where susceptible persons with no direct contact with the index patient have acquired infection. 1
• This route is far less efficient than with chickenpox and typically requires enclosed healthcare environments with concentrated exposure. 1
• Nosocomial transmission has occurred through patients, hospital staff, and visitors infected with herpes zoster, highlighting the importance of airborne precautions in healthcare settings. 1

Critical Distinction: What Shingles Can and Cannot Transmit

A person with shingles cannot give another person shingles directly—they can only transmit VZV, which causes chickenpox in susceptible individuals who have never had chickenpox or the varicella vaccine. 1

• Shingles itself occurs only as a reactivation of latent VZV that remains dormant in sensory ganglia after primary varicella infection. 2
• The virus establishes latency in dorsal root ganglia during the initial chickenpox infection and reactivates when cell-mediated immunity declines. 2, 3

Contagious Period

Timeline of Infectivity

• The period of contagiousness begins 1-2 days before the onset of rash and continues until all lesions have dried and crusted, typically 4-7 days after rash onset. 1
• For lesions that do not crust (macules and papules), contagiousness ends when no new lesions appear within a 24-hour period. 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. 1
• These patients have slower lesion healing and prolonged viral shedding, extending the time required for lesions to become fully dried and crusted. 1
• Without prompt antiviral therapy, the risk of disseminated varicella-zoster infection rises to 10-20% in immunocompromised individuals. 1

High-Risk Populations Who Should Avoid Exposure

Individuals with active shingles should avoid contact with:

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

Infection Control Precautions

For Immunocompetent Patients with Localized Herpes Zoster

• Standard and contact precautions are sufficient, with complete lesion coverage and maintenance of at least 6 feet physical separation from other patients. 1
• The patient should wear a surgical mask to prevent droplet transmission. 1
• Airborne precautions are not required for immunocompetent patients with localized disease. 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 rooms are 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

Common Pitfalls to Avoid

• Assuming that starting antiviral therapy immediately makes the patient non-contagious—viral shedding continues until lesions are fully crusted, regardless of antiviral treatment. 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 beyond the typical 4-7 day window. 1

Practical Prevention Measures

• Patients with shingles should wash hands frequently with soap and water. 1
• Use separate towels and pillows from household members. 1
• Keep all lesions completely covered until fully crusted. 1
• Avoid sharing personal items that may contact the rash. 1