This is really interesting. As the study notes, this is not a general property of viral infections or even viral respiratory infections, and COVID is actually kinda distinctive in this regard:

Various immune challenges induce diverse immunological responses that differentially involve particular subsets of immune cells and induce disease-specific cytokine and chemokine profiles systemically and in the CNS. The differences in neuroinflammatory profiles observed here in mouse models of SARS-CoV-2 and H1N1 influenza respiratory infection underscore this principle. SARS-CoV-2 infection induces a broad inflammatory response—well beyond the typical type-1 immune response seen with other respiratory viral infections (Lucas et al., 2020). Concordantly, we find here that even mild respiratory COVID can induce prominent elevation of multiple cytokines and chemokines together with lasting reactivity of white matter microglia in subcortical and hippocampal regions. By comparison, H1N1 influenza elicited a partially overlapping but also distinct CSF cytokine/chemokine profile and more restricted pattern of persistent cellular changes.