Droplet digital polymerase chain reaction (ddPCR) was adapted for quantifying the number of orthopoxviral genomes in purified virus samples, infected cell lysates and tissues of infected animals. In contrast to the more commonly used qPCR, the newer ddPCR provides absolute numbers of DNA copies in samples without need for standard curves and has the ability to detect rare mutants in a population. The genome/infectious unit ratio for several sucrose gradient-purified orthopoxviruses varied from 5 to 10, which correlated well with values obtained using the Virocyt, a dedicated fluorescence flow cytometer. By employing a nuclease step to digest unencapsulated DNA, the genome/infectious unit ratios of virus in crude cell lysates approached that of purified virus particles. The speed, accuracy, sensitivity, and dynamic range of less than one to millions of infectious units in a sample make this semi-automated method well suited to a variety of laboratory, animal and clinical studies.

微滴数字聚合酶链式反应 (ddPCR) 适用于定量纯化病毒样本、感染细胞裂解物和感染动物组织中的正痘病毒基因组数量。与更常用的 qPCR 相比，较新的 ddPCR 无需标准曲线即可提供样本中 DNA 拷贝的绝对数量，并且能够检测群体中的罕见突变体。几种蔗糖梯度纯化的正痘病毒的基因组/感染单位比率从 5 到 10 不等，这与使用专用荧光流式细胞仪 Virocyt 获得的值密切相关。通过采用核酸酶步骤消化未封装的 DNA，粗制细胞裂解物中病毒的基因组/感染单位比率接近纯化病毒颗粒的比率。样本中少于一到数百万个感染单位的速度、准确性、灵敏度和动态范围使这种半自动化方法非常适合各种实验室、动物和临床研究。