Parents usually ask when their child can return to school after having chickenpox. The correct answer would be:

Choice A rationale This statement is not the most accurate guideline for returning to school. While fading indicates healing, the crucial infectious period ends when the vesicles have dried and formed crusts. Waiting until complete fading of all lesions is an overly conservative and unnecessary measure that would extend the exclusion period beyond the time of non-infectivity. The virus is primarily spread via direct contact and airborne droplets until the crusting stage is complete. Choice B rationale Using a fixed period like ten days after initial lesions appear is an unreliable measure because the time course of the disease, especially the crusting phase, varies among individuals. The risk of transmission remains as long as moist, open vesicles are present, regardless of the number of days that have passed since the initial rash onset. The actual measure of non-infectivity is physical crusting. Choice C rationale This is the scientifically correct guideline. The child is no longer considered contagious with chickenpox (varicella) once all vesicular lesions have dried and crusted over, as the viral load in the lesions is significantly reduced. This usually takes about six to seven days after the rash onset. School exclusion policies are based on preventing the spread of the highly contagious varicella-zoster virus to others. Choice D rationale While a normal temperature is a sign of clinical improvement and resolution of the acute febrile illness, it does not confirm that the child is no longer contagious. The contagiousness is directly related to the presence of uncrusted lesions that contain infectious viral particles. A child may be afebrile but still have uncrusted, infectious lesions, making the return to school unsafe.