Orthopoxviruses tend to have non-specific early symptoms that cannot be differentiated readily from other infectious exanthemas, such as varicella-zoster virus (VZV) or disseminated herpes simplex virus (HSV) infections. A rapid assay was developed for the differential diagnosis of orthopoxviruses and herpesviruses based upon the melting temperatures of real-time PCR amplicons. A mean melting temperature difference of 8.7 degrees C was observed between the products amplified from the two virus families. Further identification of individual pathogens was made using restriction enzyme analysis. The assay was able to identify correctly viruses from quality control panels of herpes and orthopoxviruses.