It was just reported that Aiba is being hospitalised for a week.

He had chest pains and upon consultation with the doctor is diagnosed with spontaneous pneumothorax on his left lung.
(If I remember correctly, it is the same condition he had a few years back)

Scheduled concert rehearsals and his other activities are put on hold.

Hope Aiba will get well soon. Pray and wish for his quick recovery, everyone.

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Edit 1:
Hmm... Went back to check the online news, but got error messages instead. Were the articles deleted or...?

Awaiting official clarification and press release from J-Storm and Arashi.
(Hoping this isn't really happening, but we'll see... It'll be good if this was just an erroneous hasty reporting by the news agencies. ^^)

~~~
Edit 2:

It's true.
The worrying news were picked up by the morning news shows and the articles went up online again.

The media were informed by Johnny's of Aiba's condition.
Aiba felt chest pains after filming Arashi ni Shiyagare on the night of 28th. 
Went to the hospital for a check up where the doctor diagnosed him with the spontaneous pneumothorax of his left lung.
He was immediately hospitalised for a week for bed rest and treatment.

Aiba had pneumothorax back in March 2002.
Males around his age with similar body type are more vulnerable to this condition.

Right now, there is no definite date for him to return to work yet.
They are keeping an eye on his condition and seeing how it goes.

Fans are advised not to search and go to the hospital. It wouldn't do anyone any good by loitering around the hospital.

Anyway, about why the articles went down temporarily, no explanation was given.
I think they were released too soon. On hindsight, the publishers probably thought it would be better to take them down first,
so more people would buy their newspapers in the morning. Poor timing, I'm afraid. ^^;;

Right, rest well and get better soon, Aiba! We are all hoping for your quick recovery. ^^

Good news~ Aiba's already out of the hospital. ^^

He even turned up to the VS Arashi shooting, though he didn't do anything physically demanding. He's taking it easy. ^^

Aiba said he has recovered and that he was sorry for making everyone worried and causing  inconvenience. He added that he will take care of his health so as not to cause worry again.

I hope he won't push himself too hard. Take care and be healthy, Aiba and everyone else too. ^^