Using an electron microscope, they found that the virus had the size and appearance of a poxvirus (see for electron micr用电子显微镜他们发现这种病毒有着痘病毒的大小和外观（见电子显微镜图像）。
Poxvirus is the biggest virion in nature, of which the most notorious member is Variola virus that had caused disasters 痘病毒是自然界最大的病毒，其中最著名的成员是曾给人类带来深重灾难的天花病毒，属于痘病毒科正痘病毒属。