This is the 5645th most frequent Polish word.
wirusa
"Wirusa" means "virus" in English (in the genitive case).
The word 'wirusa' is used to denote the genitive case of the noun 'wirus', indicating possession or specification (e.g., the virus in question).
Lekarz twierdzi, że wirusa należy zwalczać skuteczniej.
The doctor claims that the virus needs to be tackled more effectively.
Here 'wirusa' indicates the accusative case of the masculine inanimate noun 'wirus', showing the direct object of the action (to catch a virus).
Nie jestem pewien, jak mogłem złapać tego wirusa.
I'm not sure how I could have caught this virus.
In this sentence, 'wirusa' is in the genitive case, used after the preposition 'na temat' to specify the topic of discussion (the virus).