Piedmont Healthcare has advised the patients that they should be tested for HIV as well as hepatitis B and hepatitis C.
The concerns involve surgeries at Piedmont West Surgery Center on Howell Mill Road between May 2011 and mid-April of this year.
Piedmont said no patient has reported problems.
"As scary as it sounds, statistically the risk of transmission from something like this is actually quite remote," Dr. Leigh Hamby, Piedmont's chief medical officer, told The Atlanta Journal-Constitution.
"It's a big deal to patients getting these letters because it is potentially very frightening and starts making you think, "What if, oh my gosh, this could be a life-changing event,'" Hamby added. "I think the risk of that happening is going to be extremely low."
Piedmont said the surgery center staff cleaned the endoscopy instruments with enzymatic soap after each use. However, officials said the staff failed to perform the final recommended step of soaking the equipment in a high-level disinfectant.
The problem was discovered by a doctor who observed the cleaning practices at Piedmont West and questioned them, Hamby said.
The Atlanta-based Centers for Disease Control receives several reports a year of patients being exposed to endoscopes that were not properly sanitized, said Joseph Perz, a CDC health care epidemiologist.
The largest such case involved the Veterans Administration, in which more than 10,000 patients between 2004 and 2009 received colonoscopies with improperly cleaned equipment at numerous facilities.
Perz said there is an awareness that such cases can lead to infections.
"I think it says something for the institutions here that they are recognizing the error and trying to do right by patients," Perz told the Atlanta newspaper.
Piedmont had set up a special phone line for affected patients to call and has already begun screening them at no charge.
Information from: The Atlanta Journal-Constitution.
Copyright 2013 The Associated Press.