Drogba tests positive for malaria
Drogba is believed to have had malaria for several weeks and, having been left out of the starting line-up for the game against Liverpool as a result of a fever, tests on Monday night confirmed the presence of the disease.
However, Ancelotti revealed Drogba is now fit again and is likely to be available to face Fulham at Stamford Bridge on Wednesday.
"We found out last night when blood tests showed he had malaria," Ancelotti said. "I don't know where he got it from.
"He had a problem. He has this virus and, obviously, he lost power and training. He lost his condition. He's had treatment and now he's okay. He'll come back immediately in the best condition.
"He suffered, obviously, because he wasn't 100% but now, after treatment, he'll be better. He had malaria. He had the tests in the last day, and they showed this kind of virus. Now he's good.
"I don't know where he got it from. I gave him a few days off and he went on holiday for a few days, and then he has malaria, but it's over now. He's okay."
A spokesman for the club added: "The course of medication he is on now will clear it up in three days. This type of malaria will not come back. We are not sure where and when he picked it up.
"It can lie dormant in the body for a long time. He is safe to play with malaria.
"When he first fell ill, we treated him symptomatically. He had a virus and it has come up and gone down, and then come up again.
"We ran tests on all the tropical diseases and viruses but, because it was dormant, there was not enough parasitic activity in his blood to pick up malaria in the initial tests.
"You re-test and re-test and when the results came back last night the parasitic activity in his blood had reached a level where it showed up."