Merci bien. I was wondering why it wasn't "dû", but I didn't consider the gender. So "due" is not its own separate lexeme, it's just the feminine singular of the participle.
I did not recognize "due" as the feminine past participle of "dû."
Is there a general grammar rule that the circumflex is dropped in going from masculine to feminine?
Sometimes the circumflex distinguishes words that are otherwise spelled the same. That's the rule that applies here. "Dû" uses the circumflex to distinguish it from "du". The feminine participle doesn't require the circumflex because there's nothing to mix it up with.
In English, at least, "due to" and "caused by" are adjectival, whereas "because of," "as a result of," and "owing to" are adverbial. "Coughs due to colds" is how many people remember the subtle difference.
I happened to type "caused by" in my answer, though I would've thought "due to" would have worked, too. As the Vulcans would say, "I rejoice in our differences."
"Malady" is accepted in other places, but not here, for some reason. Rejected in both "This malady is caused by a virus," and "This malady is due to a virus."
"Malady" is a fine English word, but it is uncommon in actual use anymore. There is no reason to insert a term like that here unless you just want to push the limit of standard speech.