Herpes Zoster Contagiousness with Crusted Lesions
Once herpes zoster lesions are fully crusted and dried, the person is no longer contagious to a newborn or anyone else. 1
Understanding the Contagious Period
The critical distinction is the state of the lesions:
- Active contagiousness occurs from 1-2 days before rash onset until all lesions have completely dried and crusted, typically 4-7 days after rash appearance 1
- Transmission requires direct contact with fluid from active vesicles or, rarely in healthcare settings, airborne exposure to viral particles from uncrusted lesions 2, 1
- Crusted lesions indicate the end of viral shedding and mark the point when isolation precautions can be discontinued 1
Why Crusted Lesions Are Not Contagious
The varicella-zoster virus (VZV) is transmitted through:
- Direct contact with vesicular fluid from active, fluid-filled lesions 1
- Airborne transmission from respiratory secretions or aerosolized vesicle fluid (primarily in healthcare settings) 1
Once lesions crust over, viral shedding ceases because the virus is no longer being actively released from the skin 1. The dried crust contains no infectious viral particles capable of transmission.
Special Considerations for Newborns
While crusted lesions pose no transmission risk, newborns remain a uniquely vulnerable population for other reasons:
- Newborns whose mothers develop varicella (not zoster) from 5 days before to 2 days after delivery face severe disease risk with estimated 17-30% developing severe infection and historical mortality estimates of 31% 2
- Maternal herpes zoster during pregnancy does not cause congenital varicella syndrome, unlike maternal varicella infection 2
- The risk from herpes zoster is approximately 20% that of varicella transmission risk, making it significantly less contagious overall 2, 1
Practical Guidance
For someone with fully crusted zoster lesions around a newborn:
- No isolation or contact restrictions are needed once all lesions are completely crusted 1
- Standard hygiene practices (handwashing) remain appropriate 1
- If any lesions remain uncrusted, complete avoidance of the newborn is mandatory until all lesions have dried and crusted 1
Common Pitfalls to Avoid
- Assuming partial crusting is sufficient - ALL lesions must be completely dried and crusted before the person is non-contagious 1
- Confusing the timeline for immunocompromised individuals, who may have prolonged viral shedding (7-14 days or longer) and slower crusting 1
- Mistaking early scabbing for complete crusting - lesions must be fully dried without any moist or weeping areas 1
- Believing antiviral therapy immediately eliminates contagiousness - viral shedding continues until complete crusting occurs regardless of treatment 1