Present perfect in Japanese and English

I’m reading about present, present perfect and past tenses in Japanese and English.

'My aunt has been sick since last month'

corresponds to in Japanese, the equivalent of

'My aunt is sick from last month'

which is not grammatical?

But what about, ‘the series is continued from last season’, ‘the balance is carried over from last year,’ and …

http://books.google.com/ngrams return hits for ‘is ADJ since last’.

In Japanese you can say also,

'My aunt WAS sick from last month'

for example, if

1. She is entertaining visitors in the front room, and someone notes, You don’t look in the best of health, or

2. if she is dead.

In English for 1, you would say,

‘My aunt has been sick’

but not ‘My aunt has been sick since last month’, which you only say if she is still sick.

For 2, you can’t use present perfect with dead people. You would say,

'She was sick for a month before she died' or

'She had been sick since last month.'

You can use ‘posthumously’.

"Nelson Mandela has been posthumously awarded the Nobel Peace Price"

but not

"Nick Dickson has been posthumously elected to the Senate",

unless they intend to prop up his corpse in the chamber.

There is an incredible spike during the 1940’s for ‘has been posthumously’ on http://books.google.com/ngrams

The book I’m reading is 寺村 秀夫. 日本語のシンタクスと意味. 第2巻, くろしお出版, 1982, or so, from which the information about Japanese is taken.