If they in fact can't transmit, then this is OK. If they can or, even worse, have a long latency period and will show symptoms in 2 weeks, that is very, very scary.
Our best tool for diseases like this is contact tracing. And asymptomatic carriers make that very hard.
(Useless trivia, the first documented asymptomatic carrier who was infectious was a short order cook named Mary Mallon. She is better known as Typhoid Mary.)
When she was first identified, she cooked for a number of families. The outbreak that got her put away for life was due to working as a cook at Sloane Hospital for Women.
