noun which may take the genitive case particle 'no', noun
Medical term used attributively to describe something caused by or related to a virus, such as infections or diseases.
A viral infectious disease is going around.
These symptoms are thought to be viral in nature.
viral hepatitis
viral pneumonia
viral encephalitis
viral hemorrhagic fever
Standard spelling using ウイルス.
Alternate spelling using ウィルス; less common but still encountered.
Compound of ウイルス (virus) + 性 (nature, -ity), forming a no-adjective meaning 'viral'. The word ウイルス itself is a loanword from Latin 'virus' via German or English.