。
I hear she's seriously ill.
Literal
She [topic-は] seriously-ill [hearsay-だそうだ].
~だそうだ is the hearsay ending — the speaker is reporting information they heard from someone else, not something they know firsthand. This is distinct from the appearance/likelihood ~そうだ (which attaches to verb/adjective stems, not だ). 重病 (じゅうびょう) means 'serious illness' — 重 (heavy/serious) + 病 (illness). The sentence is a natural example of how Japanese clearly marks information source.