Zoo Atlanta says an analysis of a dead parakeet indicated the presence of psittacosis, which is also known as parrot fever or ornithosis.
It's the first known instance of this disease in the zoo's parakeet collection.
The zoo plans to test its flock and decontaminate the aviary before it's reopened to the public.
People can contract the infection if they handle affected birds or inhale bacteria from bird feces or organic debris.
Symptoms in humans are generally mild and may include fever, headache, rash, muscle aches, chills, and upper or lower respiratory tract infections.