[sadur]

'Virus' is a neuter second-declension noun, while 'corpus' and 'tempus' are third-declension nouns. So, if you want to use 'virus' in plural maybe the best form is 'vira'.

[cperciva]

'Virus' is a neuter second-declension noun

Citation needed. As far as I'm aware, there is no classical attestation for either second or third declension.