Is shingles (varicella-zoster virus infection) contagious to others, particularly those who have not had chickenpox or been vaccinated against varicella?

Is Shingles Contagious?

Yes, shingles is contagious, but only to individuals who have never had chickenpox or have not been vaccinated against varicella-zoster virus (VZV). 1

Mechanism of Transmission

• Shingles transmits VZV through direct contact with fluid from the vesicular lesions or through inhalation of aerosolized particles from these lesions. 1
• The virus cannot be transmitted through respiratory secretions in the same way chickenpox spreads, making shingles less contagious than primary varicella infection. 1
• Airborne transmission has been documented in healthcare settings from patients with either localized or disseminated shingles, resulting in chickenpox in susceptible individuals who had no direct contact with the infected person. 1

Who Is at Risk of Infection

• Susceptible individuals—those without prior chickenpox infection or varicella vaccination—can develop chickenpox (not shingles) after exposure to someone with active shingles. 1
• The secondary attack rate for varicella can reach 90% among susceptible contacts. 1
• High-risk populations requiring particular protection include pregnant women, immunocompromised patients, unvaccinated infants, and individuals without detectable VZV antibodies. 1

Contagious Period and Infection Control

• Patients with shingles remain contagious from the time vesicular lesions appear until all lesions have completely crusted over. 1, 2
• The CDC recommends that patients avoid contact with susceptible individuals until all lesions have crusted. 2
• Localized shingles is considerably less infectious than chickenpox or disseminated shingles. 1
• Disseminated shingles (involving multiple dermatomes or visceral organs) is considered as infectious as primary varicella and requires airborne precautions. 1

Special Considerations for Healthcare Settings

• Nosocomial transmission of VZV from patients with shingles has been well-documented, with airborne spread occurring even without direct contact with the index patient. 1
• Healthcare personnel and other patients who are susceptible to VZV are at risk of developing chickenpox after exposure to a patient with shingles. 1
• Delays in diagnosis or implementing isolation precautions have resulted in multiple secondary cases in hospital settings. 1

Post-Exposure Prophylaxis

• Varicella-zoster immune globulin (VZIG) should be administered to susceptible high-risk individuals within 96 hours of exposure to someone with active shingles. 1
• If VZIG is unavailable or more than 96 hours have elapsed, a 7-day course of oral acyclovir beginning 7-10 days after exposure is recommended. 2, 3
• Household contacts of susceptible HIV-infected or immunocompromised persons should be vaccinated against VZV to prevent transmission. 1

Common Pitfall to Avoid

A widespread misconception exists that shingles is not contagious or is significantly less infectious than chickenpox. 4 While localized shingles is indeed less contagious than primary varicella, it can still transmit VZV to susceptible individuals and cause chickenpox, particularly through direct contact with lesion fluid or in healthcare settings through airborne transmission. 1, 4 Healthcare providers must maintain appropriate precautions until all lesions have crusted to prevent transmission to vulnerable populations. 1, 2