Influenza viruses can spread through the air onto dust, fibers and other microscopic particles, according to new research from the University of California, Davis and the Icahn School of Medicine at Mt. Sinai. The findings, with implicit implications for coronavirus and influenza transmission, will be published today (August 18, 2020) in the journal Nature communication.
“It’s really shocking to most virologists and epidemiologists that dust with air, instead of exhaling droplets, can interact with influenza viruses that can infect animals,” said Professor William Ristenpart of the UC Davis Department of Chemical Engineering, who helped lead the investigation. “The most implicit assumption is always that the transmission takes place through the air due to respiratory droplets emitted by coughing, sneezing or talking. Substance transfer opens up entirely new areas of research and has profound implications for how we interpret laboratory experiments as epidemiological investigations of outbreaks. ”
Fomites and influenza virus
Influenza virus is thought to be spread by several different routes, including in droplets extracted from the respiratory tract or on secondary objects such as door handles or used tissue. These secondary objects are called fomites. However, not much is known about which routes are the most important. The response may be different for different strains of influenza virus than for other respiratory viruses, including coronaviruses such as SARS-CoV2.
“It’s really shocking to most virologists and epidemiologists that dust in air, instead of exhaling drops, can carry influenza viruses that can infect animals.” – Professor William Ristenpart
In the new study, UC Davis engineering student Sima Asadi and Ristenpart collaborated with virologists led by Dr. Nicole Bouvier at Mt. Sinai to see if small, non-respiratory particles they call “aerosolized fomites” can carry flu virus between guinea pigs.
Using an automatic particle sensor to count the particles of air, they found that non-infected guinea pigs produce spikes of up to 1,000 particles per second as they move around the cage. Particles emitted by the animals’ breathing were at a constant, much lower rate.
Immune guinea pigs with flu virus painted on their fur could transmit the virus through the air to other, susceptible guinea pigs, showing that the virus did not have to come directly from the airways to be infectious.
Finally, the researchers are testing whether microscopic fibers of a living thing can carry infected viruses. They treated paper facial tissues with influenza virus, allowed them to dry out, and then crawled in front of the automated particle sizer. Crumples of the tissues released up to 900 particles per second in a wide range that could be inhaled, they found. They could also infect cells from these particles released from the virus-contaminated paper tissues.
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Reference: August 18, 2020, Nature communication.
DOI: 10.1038 / s41467-020-17888-w
Additional cohorts on paper include Anthony Wexler at UC Davis and Nassima Gaaloul ben Hnia and Ramya S. Barre, all at the Icahn School of Medicine at Mount Sinai, New York.
The work was supported by a grant from the National Institute of Allergy and Infectious Diseases of the National Institutes of Health.
