American Ebola patient's son says she's getting better and doctors are 'very optimistic' about recovery
Nancy Writebol was working as a Christian missionary in Liberia when she contracted the Ebola virus
The 59-year-old aid worker was flown out of the country and is now being treated at Emory University, alongside an infected America doctor
Writebol's son Jeremy appeared on the Today show Tuesday to say his mother is now smiling and 'even joking a little bit'
He has been able to see his mother twice a day through a window in a special ward of the university's hospital