"È ancora a letto. " Who is in the bed? She? He? The man? The girl"?The boy? The baby? The lady? The dog? The cat? The snake? The spider?.........Even the Italians must ask! You must emphesize that LEI è ancora a letto.
You are right. It depends of the context we don't have here translating separate sentences
So is it normal in Italian to use the preposition "a" which translates to "to" or "at" for bed?