"He has been treated aggressively with IV fluids, antibiotics, oxygen supply and appropriate medications. He is much better," said Dimitrios Linos, director of surgery at Igeia Hospital in Athens.
Linos said the 74-year-old Wiesel could be discharged from the hospital this week.
Tests were being conducted, but there were no clinical indications Wiesel suffered from severe acute respiratory syndrome, doctors said.
Wiesel was in Greece to speak at the Foreign Ministry on human rights and foreign policy. His presentation had to be canceled.