罹患 (りかん) means "contracting (a disease) or affliction." Both `罹` (リ) and `患` (カン) are standard On'yomi readings. `罹` means to suffer from or be afflicted with, and `患` means illness or trouble. The compound specifically refers to falling ill or being affected by a disease. Misreadings like `にかん` and `らかん` incorrectly apply similar-looking kanji readings, while `りげん` misreads `患`.

罹患 (りかん) は「病気にかかること」を意味します。「罹」（リ）も「患」（カン）も標準的な音読みです。誤読の「にかん」や「らかん」は漢字の類似や音の混同による読み間違いで、「りげん」は「患」の誤読です。