NEFL and COVID-19: High levels of biomarkers for CNS lesions, such as glial fibrillary acid protein (GFAP) and neurofilament light chain protein (NfL), were found in the cerebrospinal fluid of severe and moderate cases of COVID-19 (Virhammar et al. 2020; Kanberg et al. 2021), suggesting that the astrocytes of these patients were in an active state.