At least 10 Americans who might have come into contact with the deadly Ebola virus in Sierra Leone are being flown back to the United States for observation , officials said on Saturday . The transfer comes amid concerns the citizens could have been exposed to an unidentified US health worker who recently tested positive for the disease while volunteering in West Africa . The worker was flown in a private jet to a National Institutes of Health ( NIH ) hospital on Friday . They are said to be in a serious condition . It is not clear how they became infected with Ebola , . The further 10 or more people who are being evacuated to the US are free of Ebola symptoms , said the Centers for Disease Control and Prevention . They will be returned on a non-commercial plane . Scroll down for video . Concerns : At least 10 Americans who might have come into contact with the deadly Ebola virus in Sierra Leone are being flown back to the US for observation . Above , health workers in the West African country . Treatment : The transfer comes amid concerns the citizens could have been exposed to an infected US health worker , who is now in a serious condition at the National Institutes of Health hospital ( pictured ) in Maryland . Upon their arrival , the Americans will be housed near the University of Nebraska Medical Center in Omaha , the NIH in Bethesda , Maryland , or Emory University Hospital in Atlanta , the CDC said . They will follow the center 's monitoring and movement guidelines during the virus 's 21-day incubation period . If someone shows symptoms , they will be sent to an Ebola treatment center for evaluation . More than 10,000 people have died from Ebola - mainly in Sierra Leone , Liberia and Guinea - since December 2013 , the World Health Organization says . In total , 24,000 cases have been reported . However , only a handful of these cases have been seen in the United States , Spain and Britain . On Saturday , Thomas Skinner , of the CDC , said an investigation into the infected health worker - and the possible exposure of others - was ongoing , adding more Americans may be evacuated . The NIH , where the unidentified patient is being treated , is one of just four hospitals in the US to have a biocontainment units . It also has infectious disease specialists to care for Ebola patients . Outbreak : More than 10,000 people have died from Ebola , mainly in Sierra Leone , Liberia and Guinea , since December 2013 , the World Health Organization says . Above , the number of cases and deaths in thousands . Infected : This graph shows the number of healthcare workers to have been struck down by the deadly virus . Hospital : Upon their arrival , the 10 or so Americans will be housed near the University of Nebraska Medical Center ( pictured ) in Omaha , the NIH in Maryland , or Emory University Hospital in Atlanta , the CDC said . The same facility treated US nurse Nina Pham , who was infected with Ebola while caring for Liberian patient , Thomas Eric Duncan , at a Texas hospital . Mr Duncan later died from the virus . Ms Pham , 26 , and another nurse , Amber Vinson , who was also infected have since recovered . On Friday , the CDC sent a team to Sierra Leone to investigate how the latest healthcare worker became exposed to Ebola , and determine who may have been in contact with the infected person . CDC spokesman Benjamin Haynes said the center was working out a plan with the U.S. State Department to determine who was coming back and where they will be sent on their return . Well-equipped : The CDC said that one patient was being sent to Emory University Hospital 's ( pictured ) special isolation unit , where several patients have already been treated for the life-threatening disease . Former patient : The NIH , where in the infected health worker is being treated , also cared for US nurse Nina Pham ( pictured ) , who was infected with Ebola while caring for a Liberian patient . She has since recovered . The CDC said that one patient was being sent to Emory University Hospital 's special isolation unit , where several Ebola patients have already been treated . Four others are being sent to Nebraska Medical Center to be near their special isolation unit in case they develop Ebola symptoms . Ebola is spread through close contact with the bodily fluids of an infected person . The virus can cause lethal bleeding , muscle aches , severe vomiting and diarrhea . The disease typically takes hold two to 10 days after exposure , but the full inoculation period is considered to last 21 days .
At least 10 American citizens are being flown back to US , CDC has said . Will be evacuated on non-commercial plane and monitored for 21 days . Comes amid concerns they were exposed to Ebola-stricken aid worker . Unnamed American worker remains in NIH hospital in serious condition . Citizens will be housed near hospitals in Omaha , Maryland and Atlanta . CDC said investigation is ongoing ; more Americans might be evacuated . Ebola disease has killed 10,000 people since December 2013 , WHO says .