The doctor, the first Italian to contract the virus, still has a fever of around 38.5 degrees but has "no new symptoms of the disease" and is "responding well to treatment", Corriere reported.
"Psychologically, he’s a strong person", Nicola Petrosillo, a medic from Rome’s Lazzaro Spallanzani Institute, was quoted by Ansa as saying.
On Tuesday, the doctor started treatment with an experimental drug after being flown back to Italy from Sierra Leone on Monday night.
The drug being used is yet to be approved for general use, although it has been tried in other Ebola cases in the United States and elsewhere in Europe.
"He has started a specific anti-viral treatment with a non-approved drug, the use of which was authorised by the Italian Medicines Agency with the approval of the health ministry," Emanuele Nicastri, the doctor in charge of the treatment, said on Tuesday.
The man has not been formally identified but Emergency, the medical NGO he was working for, said he was a 50-year-old infection specialist and Italian media described him as a married father of two daughters from Sicily whose first name is Fabrizio.
He had been working at a clinic for Ebola victims in Lakka when he contracted the disease, which has killed nearly 5,500 people in its latest outbreak in west Africa.
He spoke to his daughters by telephone before landing in Rome, telling them "he was fine, not afraid, and sure he will pull through," Italian media reported his wife as saying.