Median (IQR) 384 (155–574) days after COVID-19, median (IQR) serum neurofilament light chain (NfL, a marker of axonal injury), and glial fibrillary acidic protein (GFAP; a marker of astrocyte injury) were significantly raised in patients who had had COVID-19 compared with healthy controls (healthy control versus COVID: NfL 5.46 (3.66–10.5) versus 12.4 (9.2–18.0) pg ml−1 (U = 2,151, estimate (CI) = 5.84 (4.09 to 7.54), effect size = 0.41, P < 0.001) and GFAP 42.4 (33.3–69.6) versus 94.3 (65.6–128.2) pg ml−1 (U = 1,824, estimate (CI) = 43.4 (31.2 to 56.8), effect size = 0.46, P < 0.001)). The gene discussed is GFAP; the disease is COVID-19.