症状がある
症状を呈する

have symptoms
show symptoms
フレーズ
※ほかにも表現があると思うので、見つけたら追加してください。

It’s very possible that even if you have the virus, you will never be tested for it. This is frustrating to people who have symptoms and want to know if they should isolate themselves and warn their friends about exposure.
https://www.nytimes.com/article/symptoms-coronavir...

How should I self-isolate if I am showing symptoms?
https://www.theguardian.com/world/2020/mar/25/coro...

have[show] symptomsと複数形で使うことに留意。