FRIDAY, Feb. 25 (HealthDay News) -- Most patients struggling with a progressive and fatal form of lung disease called idiopathic pulmonary fibrosis do not risk a worsening of their condition as a result of exposure to a viral infection, new research indicates.

The finding contradicts prior investigations that had suggested viral infections might rapidly advance disease in patients diagnosed with idiopathic pulmonary fibrosis (IPF).

"The results of this study suggest that the majority of cases of acute exacerbation of IPF are not due to viral infection," study author Dr. Harold Collard, director of the Interstitial Lung Disease Program at the University of California, San Francisco (UCSF), said in a news release from the American Thoracic Society.

Collard and colleagues from the United States, Korea and Japan report their observations online in advance of publication in an upcoming print issue of the American Journal of Respiratory and Critical Care Medicine.

The authors noted that IPF is characterized by the thickening and scarring of the lungs, and most often affects men and women in their 50s, 60s and 70s.

The stiffening of lung tissue that occurs in those with the disease ultimately compromises respiratory function. In some cases, the ongoing and debilitating process unfolds slowly. However, in others, a more aggressive process takes hold in the form of an "acute" phase with more rapid consequences.

To see whether or not a viral infection might trigger the onset of this acute process, between 2006 and 2009, Collard's team focused on 43 patients from two health facilities, all of whom had already been diagnosed with the harsher and speedier form of the disease. For comparison, 69 patients from a different medical center were also included, all of whom were diagnosed with either the slower-moving ("stable") form of IPF or, alternatively, an acute lung injury.

After collecting lung fluid and blood samples from all of the patients, the investigators performed a series of high-tech DNA tests to look for signs of viral infection.

The results: while no evidence of viral infection was found in the "stable" IPF patients, only four of the "acute" IPF patients were infected with a tell-tale common respiratory virus.

"The presence of respiratory viral infections in these four IPF patients suggests that a small minority of acute exacerbations of IPF may be caused by occult infection with common respiratory viruses," said Collard, who is also an assistant clinical professor of medicine at UCSF.

Unexpectedly, however, the authors also found that about one-quarter of both the acute IPF group and the acute lung infection group were infected with a common, typically symptomless virus known as the torque teno virus, or TTV. The virus was not found among any of the stable IPF patients.

The team cautioned that more research is needed to determine in what way TTV infection (which is usually associated with hepatitis) might be linked to IPF.

More information

For more on idiopathic pulmonary fibrosis, visit the U.S. National Heart, Lung and Blood Institute.