Test results for the patient "were positive for Lassa fever," Centers for Disease Control and Prevention spokesman Benjamin Hayes said.
Doctors had suspected the patient, an American physician assistant who'd been working with a missionary organization in Togo, had the virus. At the request of the U.S. State Department, the individual was transported from West Africa to the Atlanta hospital for treatment.
The patient is being treated at the university's Serious Communicable Diseases Unit, where four U.S. patients were treated for Ebola in 2014.
"We are continuing to treat the patient for symptoms of febrile illness," Emory spokeswoman Holly Korschun said.
What is Lassa fever?
Lassa fever is a virus spread by rats that is endemic in Sierra Leone, Liberia, New Guinea and Nigeria, according to the CDC.
Symptoms can be similar to Ebola, including hemorrhagic fever and bleeding, although 80% of patients experience mild symptoms and can even go undiagnosed, according to the World Health Organization
Lassa fever is deadly in about 1% of all individuals. Among those who require hospitalization for their illness, 15% do not survive.
Unlike Ebola, Lassa fever is not spread from person to person. People become infected from contact with urine or feces of an infected rat, which sometimes happens from food. Breathing particles in the air from infected rat feces can also lead to infection. Coming into direct contact with bodily fluids from an infected person can also lead to infection, although this is rare.
Symptoms begin one to three weeks after a person is infected.
The virus can be treated with the antiviral drug Ribavirin
Lassa fever infects an estimated 100,000 to 300,000 people in West Africa each year and is responsible for 5,000 deaths.
There have only been six cases of Lassa fever in the United States, according to the CDC. All were infected while traveling to countries where the virus was spreading.
The most recent case was in May 2015
, when a man who had returned from traveling to Liberia died from Lassa fever in a New Jersey hospital.