noun, noun which may take the genitive case particle 'no'
high virulence; strong toxicity
Medical term describing a pathogen or substance with a high degree of virulence or toxicity. Often used attributively with の.
このウイルスは強毒性の株です。
This virus is a highly virulent strain.
強毒性の化学物質
A highly toxic chemical substance was detected.
弱毒性 is the antonym, meaning 'low virulence' or 'weak toxicity'.
Compound of 強 (strong) + 毒性 (toxicity). The exact historical derivation is uncertain, but the word follows a common pattern for technical terms.