Donald Trump has expressed concern over news that an Ebola patient will be flown to a specialized isolation unit at an Atlanta hospital, NBC News reports.

The billionaire took to Twitter to suggest that American borders should be closed to anyone with the virus that has killed hundreds of people in West Africa. That would apparently include two U.S. citizens — a doctor and a missionary — who are fighting for their lives in Liberia, according to NBC News.
 

“Stop the EBOLA patients from entering the U.S. Treat them, at the highest level, over there. THE UNITED STATES HAS ENOUGH PROBLEMS!” Trump tweeted.
 

Some of the replies noted health officials say the unit at Emory University Hospital was built specifically to contain a disease like Ebola, and that the virus is not as easily transmitted as the flu.
 

Thomas Frieden, director of the Centers for Disease Control and Prevention, said that even if Ebola were to arrive in the U.S., it could be stamped out and poses little risk to the general population.