By Maggie Fox
Health and Science Correspondent
WASHINGTON (Reuters) - Simply inhaling a saltwater spray could help prevent the spread of diseases including flu and tuberculosis, U.S. and German researchers reported on Monday.
They found a saline spray, administered using a device called a jet nebulizer, reduced the number of germ-spreading droplets by as much as 70 percent for six hours.
The findings, published in the Proceedings of the National Academy of Sciences, could provide a way to help control epidemics such as the 2003 outbreak of Severe Acute Respiratory Syndrome that spread globally and killed many health care workers trying to help patients.
The findings might also help control any global influenza pandemic, which almost all health experts believe is coming and which could kill millions.
The researchers noted much more study was needed before a saline spray device could be marketed to prevent the spread of diseases.
Gerhard Scheuch of Harvard University and colleagues there and at biotechnology firms Pulmatrix and Inamed tested 11 volunteers, giving them the oral spray and then measuring how many particles they released when coughing.
"Viruses known to spread from humans and/or animals through breathing, sneezing, and coughing include measles, influenza virus, adenovirus, African swine fever virus, foot and mouth disease virus, Varicella zoster virus (chickenpox), infectious bronchitis virus and smallpox, among others," they wrote.
Bacteria spread in airborne droplets include anthrax, Escherichia coli and tuberculosis.
Scheuch's team noted some people produced many more little droplets or bioaerosols than others -- something also seen by investigators of the SARS outbreak that spread from China to cities around the world, killing 800 people.
Such "super-spreaders" were responsible for several clusters of the often deadly viral infection.
That may mean that about half the population generally may produce more than 98 percent of all disease-spreading droplets, the researchers said.
"We found a sharp demarcation between individuals who are 'high' and 'low' producers of bioaerosols, small droplets of fluid exhaled from the lungs that may carry airborne pathogens," said David Edwards, a professor of biomedical engineering at Harvard, who worked on the study.
"Roughly half our subjects exhaled tens of bioaerosol particles per liter, while the other half exhaled thousands of these particles. The number of exhaled particles varied dramatically over time and among subjects, ranging from a low of one particle per liter to a high of more than 10,000."
They noticed that when volunteers breathed with their mouths open, as some people do habitually and which cold sufferers often must do, more droplets were spread than when they coughed or sneezed.
After the volunteers inhaled a salt spray via the nebulizer for six minutes, those prone to producing the most droplets saw a reduction of as much as 70 percent, the researchers said.
The saline seems to affect the surface tension of fluid inside the lungs, they found. Surface tension is a physical property of fluids that allows some bugs to walk on water, for instance, and that causes water to form droplets.