The case was confirmed by the Atlanta-based Centers for Disease Control and Prevention.
Dr. Elizabeth Ford, head of Georgia's Division of Public Health, said at a news conference that the woman had traveled to Cancun, Mexico earlier this month. The woman then went home to Kentucky before traveling to western Georgia for a wedding. The woman is from Bowling Green, said Gwenda Bond, spokeswoman for the Kentucky Department of Public Health.
The friend who traveled with the woman to Mexico, as well as friends and family who were with her in Georgia, have shown no swine flu symptoms and have received anti-viral treatments, Ford said. That includes the woman's 5-year-old daughter, who was in the car with her as she drove from Kentucky to Georgia.
The woman was admitted to West Georgia Medical System in LaGrange on Sunday with "flu-like symptoms," said medical system president and CEO Jerry Fulks. She has been treated in isolation in a "negative pressure room," which means the air is sucked out of the room through filters to remove airborne pathogens, Fulks said. Nurses and doctors caring for her are wearing masks, gloves and gowns.
Fulks described her condition Thursday afternoon as "stable."
"She is beginning to show some modest signs of improvement," he said. "But she is still very seriously ill."
The woman arrived in Mexico on April 17. She began to feel ill the next day - with fever, chills and headache - but initially thought it was because she'd gotten too much sun. She flew home to Kentucky on April 21. Two days later, she drove to Atlanta, where she shopped on April 23 and 24. She went to LaGrange for the rehearsal dinner on Saturday and to the wedding on Sunday. She went to the emergency room later that day.
Health officials are contacting people who were at the wedding to let them know they may have been exposed to swine flu, and the CDC is doing a flight investigation to notify people who may have been on the same flights back from Mexico, Ford said. Officials said they don't know where she shopped or stayed in Atlanta and aren't making any effort to contact people who may have come into contact with her here.
They encourage people who experience flu-like symptoms to see a doctor.
The state lab was still awaiting test results Thursday afternoon from 24 other cases that could be swine flu.
"We are being very mindful of trying to contain the level of panic," Ford said. There were no immediate plans to close schools or cancel public gatherings, she said.
Ford added that people should take the same precautions they would take during the normal flu season: wash hands often, cover their sneezes and stay home from school or work if they feel sick.
Georgia Gov. Sonny Perdue also urged people not to panic.
"The State of Georgia has worked diligently over the past several years to prepare for a situation like this, and we are partnering with local and federal officials to respond appropriately," he said in a statement.
The World Health Organization has raised its alert level to Phase 5, the second-highest, indicating a pandemic may be imminent.
Swine flu has symptoms nearly identical to regular flu - fever, cough and sore throat - and spreads like regular flu, through tiny particles in the air, when people cough or sneeze.
People with flu symptoms are advised to stay at home, wash their hands and cover their sneezes.
The CDC is reporting 109 confirmed cases in 11 states. Georgia's case is no included in those counts.