Aerosolized viruses can circulate in larger doses than previously thought

A Virginia Tech study has found that aerosolized flu viruses, which can remain airborne for hours, circulate in places like daycare centers, doctor's offices and airplanes in doses that are large enough to cause infection.

The study, along with two other recent studies on airborne flu transmission, may be able to provide researchers with more information on the role of the smallest flu particles, CIDRAP News reports.

To date, most evidence shows that the flu spreads most when the larger respiratory droplets dispersed over a short time and distance around an infected person contact others. Some experts believe that these smaller airborne particles may also play important roles based on how infection patterns spread in environments like airplane cabins.

The research team assessed the concentration of flu viruses in public places by collecting air samples. They then used quantitative reverse-transcriptase polymerase chase reactions to detect genetic evidence of influenza A viruses, CIDRAP News reports.

Half of all the air samples collected contained aerosolized flu viruses. The average concentration of flu virus particles in the aerosolized flu virus air was 16,000 viruses per cubic meter of air. Most of those, the studied found, were fine particles.

"Given those concentrations, the amount of viruses a person would inhale over 1 hours would be adequate to induce infection," Linsey Marr, an associate professor of civil and environmental engineering said, according to CIDRAP News.

The highest concentration of airborne particles was found at the daycare center, which was two times higher than the health center.

"Considering that children are the primary susceptible population of influenza, the difference is not surprising," the report stated, according to CIDRAP News.

Flu transmission expert and microbiologist Dr. Raymond Tellier believes that the study is important to the clarification of controversial questions related to flu spread.

"Particularly welcome also is a thorough analysis of the infectious risk unearthed by these observations, and a discussion pointing to the negligible risk of surface contamination by the aerosolized viruses," Tellier said, CIDRAP News reports.