Viruses (and a few other taxa) always show in Unknown.
https://forum.inaturalist.org/t/non-iconic-taxa-appear-under-unidentified-unknown-observations/702
https://forum.inaturalist.org/t/ided-species-turns-up-in-identify-with-unknown-filter/5188
https://forum.inaturalist.org/t/genus-nostoc-showing-in-search-for-unknown/8931
It’s a known issue going back to at least 2016:
https://github.com/inaturalist/inaturalist/issues/1150