http://www.italki.com/question/330070__________(7)种类和形态 http://www.italki.com/question/330055__________(5)造成因难 你自己提过 “拆分开的 类似的 ”句子的问题，现在它们合在了一起，试试自己解决。

I don't know how to translate it cause of my poor English. 病毒的种类：virus type: DNA, RNA, Prion and so on. 病毒的形态：morphology of virus: Baculovirus, spheric viruses, coronavirus and so on. One drug maybe can kill one or two or more morphology of virus, but when a new Virus subspecies is appeared, it is nearly as a new virus, you maybe have to develop a new drug to kill it, so the more morphology or types the virus has, the more difficult the drug develop.