「軽症」は mild を使って言えます。
例:
Her symptoms from the Coronavirus are quite mild still.
「彼女のコロナウイルスの症状はまだかなり軽症だ。」
symptom「症状」
「重篤」は critical と言います。
例:
He's in critical condition in the ICU.
「彼は重篤な状態でICUに入っている。」
「重症」は severe と言います。
例:
He may have to be hospitalized because his Coronavirus symptoms are quite severe.
「彼のコロナウイルスの症状はかなり重症で、もしかしたら入院しないといけないかもしれない。」
be hospitalized で「入院する」
ご参考まで!
例文一:
I caught a cold but the symptoms were minor so I didn't take a day off.
私が風邪を引いたが軽症だったので、仕事を休まなかった。
例文二:
I caught a cold but the symptoms were mild so I didn't take a day off.
私が風邪を引いたが軽症だったので、仕事を休まなかった。
例文三:
I caught a cold but the symptoms were light so I didn't take a day off.
私が風邪を引いたが軽症だったので、仕事を休まなかった。
・上記の例文では"symptoms were ~"の言い方をしましたが、"it was ~"も言えます:
"I caught a cold but it was minor so I didn't take a day off."
"I caught a cold but it was mild so I didn't take a day off."
"I caught a cold but it was light so I didn't take a day off."
・"minor/mild/light cold"の言い方にしたいなら、下記のような例文になります:
"I caught a minor cold, and didn't take a day off."
"I caught a mild cold, and didn't take a day off."
"I caught a light cold, and didn't take a day off."