structural:summarization, information:filtering, linguistic:voice_change
Viral infections

The most common cause of permanent hyposmia and anosmia are upper respiratory infections. Such dysfunctions show no change over time and can sometimes reflect damage not only to the olfactory epithelium, but also to the central olfactory structures as a result of viral invasions into the brain. Among these virus-related disorders are the common cold, hepatitis, influenza and influenza-like illness, as well as herpes. Notably, COVID-19 is associated with olfactory disturbance. Most viral infections are unrecognizable because they are so mild or entirely asymptomatic.