Avian influenza is caused by an orthomyxovirus, or influenza virus. Viruses in this group vary widely in their pathogenicity or virulence.是什么意思_Avian influenza is caused by an orthomyxovirus, or influenza virus. Viruses in this group vary widely in their pathogenicity or virulence.在线翻译_英语_读音_用法_例句