Schalke have dismissed reports that their Cameroon international, Joel Matip, has contracted malaria.
The 19-year-old midfielder has been suffering from abdominal pains and fever, and the Cologne-based newspaper Express claimed Matip had malaria.
But Schalke's media officer, Rolf Dittrich, has allayed fears he is suffering from the illness.
"Joel Matip is not doing training at this moment, he is ill," he told Sportinformationsdienst.
"However, we can rule out the illness is malaria."
Matip played for Cameroon in their 1-0 win over DR Congo on Saturday and returned to Schalke afterwards.
The Bochum-born youngster, who has now made seven international appearances for his father's homeland, was handed his Bundesliga debut by Felix Magath last November.
Matip has played in each of Schalke's seven Bundesliga games so far this season and last week signed a professional contract with the club until June 2013.