David and Nancy Writebol

An aid group says a second American aid worker has been released after she was treated at an Atlanta hospital for the Ebola virus.

The group SIM says Nancy Writebol was discharged from Emory University Hospital on Tuesday.

A news conference was planned for 11 a.m. Thursday at Emory to discuss the discharge of Writebol and another aid worker, Dr. Kent Brantly. The aid group he worked for says he was expected to be released Thursday.

Brantly and Writebol were flown out of the west African nation of Liberia earlier this month and were treated for the deadly disease in an isolation unit at the hospital.

The two were infected while working at a missionary clinic outside Liberia's capital.