Varicella, commonly known as chickenpox, is a highly contagious disease caused by the varicella-zoster virus (VZV). The characteristic skin rash is the most visible sign, but the primary public health concern is how easily the virus spreads within group settings like schools and daycares. Exclusion policies are implemented to prevent an infected child from transmitting the virus to susceptible classmates and staff members. The critical factor determining a child’s return is the point at which they are no longer able to transmit the virus.
Identifying the Contagious Window
The contagiousness of varicella begins well before the first blister is noticed on the skin. An infected person can spread the virus starting about one to two days before the signature rash appears. This pre-rash period, known as the prodromal phase, often includes mild symptoms like a slight fever and general malaise, but the child is already shedding the virus.
Transmission occurs through direct contact with the blisters or through airborne respiratory droplets released when the child coughs or sneezes. The infection remains highly contagious throughout the phase where new fluid-filled blisters are forming. The risk of transmission continues until the skin lesions have progressed to a non-infectious state.
Mandatory Criteria for Returning to School
The standard for a child’s return to school or daycare is centered on the progression of the skin lesions. A child with an uncomplicated case of varicella is safe to return only when all lesions have formed dry crusts, or scabs. This crusting process signals that the virus is no longer actively shedding.
This criterion applies to all spots, including those that may be hidden on the scalp, inside the mouth, or in the genital area. For a typical, unvaccinated case of chickenpox, this process usually takes about four to seven days after the rash first appears. An additional requirement is that the child must be fever-free for a specified period, generally 24 hours, without the use of fever-reducing medication.
Breakthrough Varicella
For children who have been vaccinated and develop a mild case, often called breakthrough varicella, the lesions may not progress to the point of forming a crust. In these milder cases, the child is considered non-contagious and can return to school when no new lesions have appeared for at least 24 hours.
When Varicella Complications Delay Return
While the scabbing of all lesions marks the end of the contagious period, certain complications can delay a child’s return to the classroom. The most common complication is a secondary bacterial infection of the skin lesions, presenting as impetigo or cellulitis. These bacterial infections require antibiotic treatment and can significantly delay healing, meaning the child must remain home until the infection is resolved and any open sores are healed or crusted.
In rare but more severe cases, varicella can lead to complications affecting internal organs, such as pneumonia or neurological symptoms like encephalitis. A child recovering from such an illness would be kept home long after the primary rash has crusted to ensure a full recovery, and their return is determined by the healthcare provider. For any severe, unusual, or protracted case, the school may require a note from a healthcare provider confirming the child is no longer infectious and is well enough to fully participate in school activities.