Centers for Disease Control and Prevention, Ch. 21: Varicella, in Atkinson W, Wolfe S, Hamborsky J (a cura di), Epidemiology and Prevention of Vaccine-Preventable Diseases, 12th, Washington DC, Public Health Foundation, 2012, pp. 301–323 (archiviato dall'url originale il 12 giugno 2012).
«The virus has not been isolated from crusted lesions.»