die Erkrankung
illness
The state of being sick; a specific disease or ailment.
Die Grippe ist eine ansteckende Erkrankung der Atemwege.
The flu is a contagious illness of the respiratory tract.

illness
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illness
The state of being sick; a specific disease or ailment.
Die Grippe ist eine ansteckende Erkrankung der Atemwege.
The flu is a contagious illness of the respiratory tract.

The noun 'Erkrankung' (illness) comes from the verb 'erkranken' (to fall ill). The prefix 'er-' often indicates the beginning of a process (becoming sick), and the ending '-ung' turns the verb into a noun.
Nach seiner schweren Erkrankung musste er sich lange erholen.
After his serious illness, he had to recover for a long time.
The word 'Erkrankung' (illness) is often used in medical, scientific, or formal contexts. It often sounds more official than the word 'Krankheit' (disease/illness).
Der Arzt diagnostizierte eine seltene Erkrankung des Immunsystems.
The doctor diagnosed a rare illness of the immune system.
'Erkrankung' (illness) is often combined with adjectives that describe severity or course, for example: 'eine schwere Erkrankung' (a serious illness), 'eine chronische Erkrankung' (a chronic illness), or 'eine psychische Erkrankung' (a mental illness).
Krebs ist eine ernsthafte Erkrankung, die früh erkannt werden sollte.
Cancer is a serious illness that should be detected early.
To describe which body part or system is affected, the genitive is often used. This sounds very precise and is common in specialist texts.
Er leidet an einer Erkrankung der Atemwege.
He suffers from an illness of the respiratory tract.
health
'die Gesundheit' and 'die Erkrankung' are opposites in meaning. 'Gesundheit' means the good state in which the body and mind are, as far as possible, not under strain. 'Erkrankung' means an illness, or the beginning and course of becoming ill. 'Erkrankung' sounds somewhat more medical and precise than 'Krankheit' (illness / disease). It is often used when talking about a specific diagnosis, treatment, or course of an illness. 'Gesundheit', by contrast, is the general positive state that you want to maintain or improve.

Die Ärztin erklärte die Erkrankung ruhig und verständlich.
The doctor explained the illness calmly and clearly.
Im Urlaub achtet Maria besonders auf ihre Gesundheit.
On vacation, Maria pays special attention to her health.