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Marr leads study on airborne flu virus

    Marr leads study on airborne flu virus

BLACKSBURG, Va.,– A parent’s wise advice to never go to a hospital unless you want to get sick may be gaining support from recent scientific studies on a specific airborne virus. 

The results of a Virginia Tech study by environmental engineers and a virologist on the risk of airborne infection in public places from concentrations of influenza A viruses is appearing today in the online, Feb. 2 issue of the United Kingdom’s Journal of the Royal Society Interface. 

Linsey Marr, associate professor of civil and environmental engineering at Virginia Tech; and her colleagues, Wan Yang, of Blacksburg, Va.; one of her graduate students; and Elankumaran Subbiah, a virologist in the biomedical sciences and pathobiology department of the Virginia-Maryland Regional College of Veterinary Medicine conducted their research in a health center, a daycare facility, and onboard airplanes. 

“The relative importance of the airborne route in influenza transmission — in which tiny respiratory droplets from infected individuals are inhaled by others — is not known,” Marr, who received a National Science Foundation CAREER Award to pinpoint sources of unhealthy air pollutants, said. 

What is known is that influenza A viruses are “transmitted through direct contact, indirect contact, large respiratory droplets, and aerosols that are left behind by the evaporation of larger droplets,” they reported in the journal. “The aerosol transmission route is particularly controversial since there is scant proof of infection mediated by virus-laden aerosols, partly due to the difficulties in studies involving human subjects and partly due to the challenges in detecting influenza A viruses in ambient air.

” What happens is an infected person might cough or sneeze or just be engaged in conversation, and release the viruses into the air. However, these aerosols are quickly diluted to very low concentrations by the surrounding air. 

Marr said, “Few studies have measured actual concentrations of influenza A viruses in air and determined the size of influenza-laden particles. Size is important because it determines how long the particles will remain suspended in the air before being removed due to the forces of gravity or other processes.” 

Incorporating the concentrations of influenza A viruses and breathing rates, Marr and her colleagues estimated the inhalation dose incurred by someone in the same room and concluded that it was sufficient to induce infection. 

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~ Lynn Nystrom