The transcription level of PD‐L1 increased and reached a peak on the 5th day after infection in the olfactory bulb (p = 0.0025), brainstem (p = 0.0141), and cerebrum (p = 0.0448), and there was a significant increase in the cerebellum from the 3rd day (p = 0.0154). The gene discussed is CD274; the disease is infection.