The New York City doctor who contracted Ebola is improving and remains in stable condition, health authorities said.

Craig Spencer contracted the disease in Guinea, West Africa where he traveled with the organization Doctor Without Borders to help combat the Ebola epidemic, Bloomberg reports. Spencer's treatment included an experimental drug and a blood transfusion from another Ebola survivor. 

When Spencer first returned, he showed no symptoms for nearly a week, leading him to come in contact with numerous people.  Two of the three people Spencer had close contact with around the time he started to show symptoms have been released from quarantine. The other remains confined.

Health officials said in a statement Wednesday that one of those people who had been under quarantine "poses no public health threat and is showing no symptoms."

"This person's daily movements in New York City will no longer be restricted, and the individual will be assessed twice each day by Health Department staff," the statement said.

Still, 357 individuals are being monitored as part of a nationwide effort to stop or quickly identify new infections. The group of people being monitored includes emergency medical workers who transported Spencer to Bellevue Hospital Center and people who recently arrived in New York from Ebola-affected countries.

The U.S. Centers for Disease Control and Prevention has said that anyone coming from nations with Ebola outbreaks will be monitored for three weeks to check if they develop symptoms, according to Bloomberg.

In September, an infected Liberian man arrived at an emergency room in Dallas with Ebola symptoms. The hospital failed to identify the disease leading to the death of Thomas Eric Duncan and prompting a call for tighter screening procedures.

The Ebola outbreak has infected about 13,000 people and killed almost 5,000. While trials for an Ebola vaccination are underway, there is no approved cure for the disease.

The disease broke out in three West African nations: Liberia, Sierra Leone and Guinea.