What kind of accusative?

[Asterisk1234]

καιπερ νοσων χαλεπην νοσον εισ την αγοραν ηλθε. (M. p. 227)
What kind of accusative is "χαλεπην νοσον"?
The key translates the sentence as "Although he was sick with a serious disease, he came to the agora"
The accusative of respect doesn't seem to fit. What then?

Thanks to all,

[jeidsath]

Cognate

[polemistes]

When a part of the sentence seems out of place, like the accusative expression here, it is generally a good idea to check LSJ to see if a verb takes such an expression. If you look up νοσέω you will immediately see that it takes acc.cogn. (e.g. νοσῶ νόσον). So the verb νοσέω works quite differently from the English ail or "be sick", which would need a preposition "from" or "with", respectively, to express the same.