He said: "My priority is that Norway has the best possible road cycling team in London but unfortunately I can't compete as my body is not functioning at its highest level."
His manager, Atle Kvålsvoll, told AFP: "There is something in his body that is making it not react like it should. I don't know whether it's a virus or something else but we are trying to find the cause."
Last month the health problem forced Hushovd out of the Tour de France.
Hushovd's place in the Norwegian team will be taken up by Vegard Stake Laengen.