Cameroon and Osasuna striker Pierre Webo has contracted malaria and will remain in hospital for about 10 days.
It means that he will miss the start of the Spanish season.
"This morning it was confirmed that the player has malaria and will not be able to begin
training for another three to four weeks," the club wrote on its website on Wednesday.
Webo picked up malaria during a visit to Cameroon in June.
Osasuna have qualified for the third qualifying round of the Champions League after finishing fourth last season.
