Washington: An American doctor who was exposed to the Ebola virus in Sierra Leone was admitted to a clinic on Sunday at the National Institutes of Health outside Washington. 

The patient, whose identity was not revealed, volunteered as a doctor in a processing unit of the suffering of tropical fever that has killed more than 3,000 people in West Africa since the end of last year .. 

"Out of an abundance of caution, the patient has been admitted to a special unit of clinical trials at the Clinical Center of the NIH that is specifically designed to provide isolation capabilities of high level and is staffed by infectious diseases and intensive care specialists "said medical research center in a statement. 

"The unit staff is trained in the practices of strict infection control optimized to prevent the spread of potentially transmissible agents such as Ebola." 

He emphasized that the patient's treatment in the United States "presents minimal risk" to other 
patients, NIH staff and the public. 

Two American doctors and a Christian missionary infected with Ebola virus in Liberia were transferred back to the United States for treatment and has since been recovered. 

Global health experts have agreed that blood therapies and convalescent sera can be used to combat Ebola immediately, while safety tests begin to potential vaccines. 

There is no medicine or vaccine on the market for treatment of Ebola. 

Ebola is transmitted by direct contact with body fluids of an infected person. The virus causes fever, vomiting, diarrhea and sometimes fatal bleeding. 

The Ebola epidemic has now infected more than 6,500 people in West Africa, killing nearly half of them, according to the World Health Organization.