A Massachusetts doctor cured of Ebola said Tuesday that he's returning to Liberia, the West African country where he contracted the virus, in January to resume working at a medical mission.

Dr. Richard Sacra said that he plans to spend four weeks at ELWA Hospital, a clinic outside Monrovia where he had contracted the deadly virus in August.

Sacra spent weeks in treatment at an Omaha, Nebraska, hospital before returning home on Sept. 25. The University of Massachusetts Medical School faculty member has worked in medical missions in Liberia for more than 20 years, including the North Carolina-based charity SIM, which founded ELWA Hospital.

Sacra, who was one of at least 10 people so far treated for Ebola in the U.S., says he "feels great" and that doctors have said he's now effectively immune to Ebola, which has no vaccine.

"I'm not hearing a lot of pushback from home," Sacra said. "I've been working there for years, and my risk at this point is no different than it was before because I'm immune to Ebola."

Sacra has said he's not sure exactly when he became infected. He had been caring for pregnant women not suspected to have Ebola and delivering babies, including performing several cesarean sections.

He said ELWA Hospital, which stands for Eternal Love Winning Africa, has changed its protocols following his illness.

"Even if we haven't suspected Ebola in that patient, we're now wearing full protective gear at our facility for deliveries," he said. "When we're doing surgeries, we're now getting bleached down at the end, which we weren't doing before."

Sacra, who expressed a desire to return to Liberia almost as soon as he recovered, made the comments following a Tuesday news conference at the Statehouse announcing a $1 million state grant to help develop a faster, more accurate test for diagnosing Ebola.

Gov. Deval Patrick said the investment, made through the Massachusetts Life Sciences Center, a quasi-public state agency, will assure the state and its major research institutions will play a central role in saving many lives from Ebola, which has killed 6,400 people during the most recent outbreak in West Africa.