Virus particles usually spread on the air through dust, fibers, and other microscopic particles, according to an investigation carried out by the University of California at Davis (United States) and published in the journal Nature Communications on Tuesday.
The findings have important implications for understanding how flu and the new coronavirus are transmitted.
The flu virus is thought to be spread indirectly from the droplets that someone breathes out or through objects called fomites, such as doorknobs or used tissues.
However, little was known about which forms of infection are the most important until now, and, depending on the type of virus (flu or coronaviruses such as SARS-CoV2), the form of infection may be different.
William Ristenpart, Chemical Engineering professor at the University of California, noted that airborne transmission was previously thought to occur due to respiratory droplets emitted by coughing, sneezing, or talking. That is why transmission through the dust “opens up entirely new areas of research and has profound implications for the way laboratory experiments and epidemiological investigations of outbreaks are interpreted”.
The research also studied whether small non-respiratory particles called “aerosol fomites” could carry the flu virus among guinea pigs.
“It is shocking to most virologists and epidemiologists that airborne dust, rather than expiratory droplets, can carry the influenza virus capable of infecting animals”, Ristenpart said.
The scientists used an automatic particle meter to count airborne particles and they found that guinea pigs could transmit the virus through the air to other specimens of their species, showing that the virus did not have to come directly from the respiratory system of the infected animal to be transmitted.
The researchers also tested the transmission of the virus through microscopic fibers. They treated tissues with the flu virus, let them dry, and then crumpled them in front of the automatic particle meter, resulting in up to 900 particles being released per second in a size range that could be inhaled.