The airborne germs causing thousands of deaths from influenza and costing billions of dollars for health care can be spread more easily in modern energy-efficient buildings, an Army study has shown.

The study, published Thursday in the Journal of the American Medical Association, found the risk of respiratory disease can be 45 percent to 100 percent higher in newer buildings.The findings were made in a 47-month study of hundreds of thousands of Army recruits housed in old and modern barracks at four basic training camps in the Southeast.

Five researchers from Walter Reed Army Institute of Research concluded the risk of catching fever and acute respiratory disease was 45 percent greater in modern barracks than in the old-style facilities where there was more fresh air and less recycled air.

During flu epidemics, the risks in modern barracks "were even more extreme, in excess of 100 percent in some cases," the researchers found.

"In tight buildings with closed ventilation systems, airborne-transmitted pathogens are not only recirculated and concentrated, but also efficiently dispersed through indoor living spaces," the researchers wrote.

"In `leaky' buildings, airborne-transmitted agents are diluted by fresh, outdoor air and relatively quickly exhausted from indoor spaces."

The old barracks were built in the 1940s or 1950s and used window and ceiling exhaust fans for ventilation. Modern barracks were built in the late 1970s or 1980s and "designed, built and operated to be energy efficient," with air conditioners recirculating 95 percent of the air.

If all recruits had been housed in old style barracks, 2,663 fewer would have had to go to the hospital for fever and respiratory ailments, the study said.

The team, led by Walter Reed's chief of epidemiology, Dr. John Brundage, noting that the common cold, rubella, measles, Legionnaire's disease, tuberculosis and other diseases are caused by airborne germs, urged engineers to consider this in the design of hospitals, schools, offices, dormitories, prisons, shelters for the homeless, day-care centers and other facilities.