HOUSTON, Oct. 14 -- A Dallas nurse diagnosed to be the second Ebola patient in the United States is now in good condition, according to Texas health authorities.

Health authorities upgraded Nina Pham, an employee at Texas Health Presbyterian Hospital, from "stable" to "good" condition on Tuesday.

The 26-year-old said in a statement that she is "doing well."

Pham is believed to be affected by Ebola virus while caring for Thomas Eric Duncan, the deceased Liberian who was known as the first Ebola patient diagnosed in the United States.

She received a blood transfusion from an American Ebola survivor who was sent home to get treatment after contracting the virus abroad. The survivor beat his own infection after receiving a similar treatment.

Pham has been kept in isolation at the hospital since Friday, two days before she was confirmed to have caught Ebola virus.

Health authorities said the one and only person who had close contact with Pham has not shown any symptoms so far. Nor has any one of some 76 medical staffers who were involved in treating Duncan.

The U.S. Centers for Disease Control and Prevention (CDC) suspect a "breach in protocol" caused Pham's infection, although it failed to pinpoint the exact kind of breach.

Health officials continue to monitor another 48 people who they believe may have had contact with Duncan before he was hospitalized. None of them has exhibited Ebola signs so far.

Pham's infection has sparked concerns about the readiness of hospitals and medical workers in handling Ebola virus, which has claimed more than 4,000 lives in West Africa.

The CDC announced Tuesday that it was organizing an Ebola response team able to reach any U.S. hospital with a confirmed Ebola patient "within hours."

The CDC also plans to improve safety at Texas Health Presbyterian Hospital in Dallas. A site manager will be overseeing infection control.