by Welkin John­son — Some­times, dis­cov­ery in bi­ol­ogy is about dis­cern­ing rules and some­times it is about pur­su­ing ex­cep­tions. In this spirit, Hu­man Her­pesvirus six (HHV‑6), the eti­o­logic agent of the com­mon child­hood ill­ness rose­ola in­fan­tum, is shap­ing up to be an in­trigu­ing ex­cep­tion. As every vi­rol­o­gist knows, mem­bers of the Her­pesviri­dae main­tain...