CHICAGO (Reuters) - The third U.S. patient to be treated in the United States for Ebola is now free of the virus, doctors at the Nebraska Medical Center and the patient said in a news conference on Thursday.

"The CDC has declared me safe and free of virus. Thank God. I love you all," Dr. Rick Sacra, 51, a Boston obstetrician who contracted Ebola while treating patients as a medical missionary at a hospital in Liberia, told a news conference.

Dr. Phil Smith, medical director of the biocontainment unit at the medical center, said the CDC confirmed that two separate blood samples taken from Sacra 24 hours apart show the virus is no longer in his bloodstream.

Sacra thanked the doctors and nurses who cared for him over the past three weeks. In a news conference, he joked that when he learned he was being flown to the Midwestern state better known for corn crops than medical care, he recalls saying,

"Wow, Nebraska. Who made that decision?" But Sacra gushed about the care he received.

"They are not only terrific medically but they are awesome in the bedside nursing and patient care," he said.

Sacra was treated with an experimental drug called TKM-Ebola made by Tekmira Pharmaceuticals Corp, and also received a "convalescent serum" made up of antibodies taken from the blood of U.S. Ebola survivor and fellow missionary Dr. Kent Brantly.

But Sacra's doctors said there was too little data to determine whether the drug contributed to his recovery.

Sacra said he feels "great except that I am extremely weak" and said he would not rule out the possibility of going back to Liberia once he is fully recovered.

Smith said the hospital has been sharing the lessons it learned in caring for Sacra with aid organizations in Africa trying to set up field hospitals as well as healthcare organizations in the United States.

Smith said the Nebraska facility was fairly well prepared to handle the large amount of infectious waste generated in the care of an Ebola patient, something that initially posed a major challenge for Emory University in Atlanta, which treated the first two U.S. Ebola patients.

Smith said the hospital's biocontainment unit is built with a pass-through sterilizer called an autoclave that allowed staff to quickly sanitize soiled sheets and used protective gear as they were removed from the patient room.

Biosafety experts told Reuters this week that most U.S. hospitals do not have large autoclave equipment and U.S. Department of Transportation guidelines prohibit waste haulers from transporting Ebola waste to an autoclave or incinerator, which may leave hospitals without a way to handle it. Smith said all of the gear used to protect staff members generates "a lot of waste," adding that it is something other providers need to plan for.

(Reporting by Julie Steenhuysen, Editing by Franklin Paul and Cynthia Osterman)