COPD is the third leading cause of death in the United States, killing as many as 120,000 people every year.

12 million Americans have been diagnosed with the condition, which some know as emphysema, or chronic bronchitis.

Millions more may have COPD, and don't realize it, but now there's hope that an antibiotic a day could help keep attacks at bay.

For 61-year-old Doug Viland, nothing beats an afternoon with his granddaughter Arianna. Keeping up with a non-stop nine-year old isn't easy, though, especially when you can't catch your breath.

"I'd take two or three steps and then I'd have to stop,” Viland said. “I'd have episodes like that all the time."

Viland has been struggling for years with COPD, a serious lung disease that clogs his airways, causing a chronic cough and a lot of phlegm. Until recently, he would often suffer a sudden, severe onset of symptoms, called a flare up.

Director of Pulmonary Diagnostic Services at the University of Michigan Health System, Dr. Fernando Martinez explained the flare ups by saying, "There's been a sense for years that these flares, in at least a group of patients with COPD, are related to bacterial infection of the lung."

Dr. Martinez is among a group of nationwide researchers studying COPD and the effects of a common antibiotic on the condition. For one year, 570 trial participants took daily doses of the drug Azithromycin, in addition to their other COPD treatments.

"We were able to demonstrate that you were able to significantly decrease, by more than 20 percent the rate of flare ups in at-risk people,” Martinez said.

The daily regimen benefits those with moderate to severe symptoms. For Viland, it made all the difference.

"Before, I could only walk about half a block. Now, I can walk up to five miles."

And that means he can keep up with his granddaughter.

Researchers say they were concerned that patients on the daily regimen would develop antibiotic resistance.

While the drugs did increase the amount of antibiotic resistant microbes in some patients, there were no infections reported.

Still, more studies will be needed to look at the long-term effects of the antibiotic treatment.