Sick visits can actually be more of a nuisance than a help.

Literal

Illness-visit [topic-は] on-the-contrary unwanted-favor [copula-だ].

病気見舞い means 'visiting someone who is sick.' かえって means 'on the contrary, instead.' ありがた迷惑 is a brilliant compound: ありがたい (grateful) + 迷惑 (nuisance) = 'an unwelcome favor' — help that's more troublesome than useful. A uniquely Japanese concept.