"I did the test because I suspected I had swine flu. The test came out positive and naturally I was shocked," the world number 17 told Bild newspaper on Tuesday.
Haas said the illness forced him to stay in his hotel room for three days with fever and chills.
"These were three very bad days. I did a test again today and I hope that by now the symptoms are out of my body so I can slowly start training again."
(Writing by Karolos Grohmann, editing by Pritha Sarkar; To query or comment on this story email sportsfeedback@thomsonreuters.com)
© Thomson Reuters 2009 All rights reserved.
