rare disease を直訳すると「珍しい病気」となります。
rare は「めったにない、珍しい」といった意味です。
「難病」に近い表現だと思います。
例）
"People around the world will be coming together to raise awareness for rare diseases
and the impact of those who are affected, so I thought maybe my school could have an
event for Rare Disease Day [on Feb. 28]," she said.
〔SILive.com-Feb 25, 2017 より〕
参考になるといいです
ありがとうございました。
it is almost incureable, a pernicious disease of the blood.
Diseases have been cured and conquered by man since modern medicine began.
However some diseases are extremely hard to"recover from" !
These can be described as " pernicious, deeply damaging and/ or malevolent"
Synonyms...we might use include: Irremediable, remediless, irrecoverable.
When you want to talk about a disease/illness/sickness that is hard to cure, then you can just explain that the disease is hard to treat/cure. Alternatively, when a disease cannot be cured, then you can say incurable disease. When not many people have an illness and it's hard to cure, then it would usually be called a rare illness.
治すことが困難な病気（disease/illness/sickness）について言う時は、disease that is hard to treat/cureと説明できます。あるいは、治すことができない病気の場合は、 incurable diseaseと言えます。治すことが困難な珍しい病気は、普通はrare illnessと呼びます。
If a disease can not be cured, it is incurable. Diseases such as HIV/AIDS, high blood pressure and diabetes are incurable but can be controlled. High blood pressure and diabetes are chronic diseases which do not get cured but are controlled so that their effects on s particular person's body do not become fatal. These diseases are incurable.
So you may say:
She is suffering from an incurable disease.
or
Diabetes and high blood pressure are chronic diseases which can lead to early death if not controlled.
治らない病気のことは「incurable（不治の）」と表現できます。「HIV/AIDS」「高血圧」「糖尿病」などは治らない（incurable）病気ですが、コントロールすることはできます。「高血圧」と「糖尿病」は治ることのない慢性的な病気（chronic disease）ですが、深刻な状態にならないようにコントロールすることはできます。これらの病気は「incurable（治らない）」です。
She is suffering from an incurable disease.
【訳】彼女は不治の病気を患っています。
Diabetes and high blood pressure are chronic diseases which can lead to early death if not controlled.
【訳】糖尿病と高血圧はコントロールしないと、若くても死に至ることのある慢性的な病気です。
We use the term "aggressive disease" when talking about a sickness that is hard to treat/cure and that spreads fast. Whereas "incurable disease" means there is no cure or way to treat the sickness and the disease may be fatal/deadly.
If someone or something is notorious, it means that it or they are well-known for doing or causing or something bad or negative.
"Dick Turpin was a notorious highwayman."
「notorious（悪名高い）」は、何か悪いものや否定的なものをしたりもたらすことで有名な人・ものを表します。
Dick Turpin was a notorious highwayman.
（ディック・ターピンは悪名高い追いはぎでした。）
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