Airborne Viruses Can Spread Through Dust And Microscopic Particles, Finds Study

Can the SARS-CoV-2, the virus that causes COVID-19, spread through dust particles? A recent study has raised this alarming possibility.

It has long been assumed that the airborne transmission of viruses, such as the one that causes COVID-19, occurs through the respiratory droplets emitted by infected person when they sneeze, cough or speak. But scientists have now demonstrated that airborne viruses can also move around via non-respiratory droplets, such as microscopic particles known as “aerosolized fomites.”

Researchers at the University of California, Davis, and the Icahn School of Medicine at Mt. Sinai showed that microscopic particles carrying the influenza virus can be generated from inanimate objects, through simple actions like rubbing a contaminated paper tissue. Their findings were published in Nature Communications.

The study did not involve the novel coronavirus. But the World Health Organization (WHO) just last month acknowledged the SARS-CoV-2 virus could be airborne, making the study's findings important in combating spread of the pandemic that has so far killed more than 780,000 people globally and infected 22.16 million.

"It’s really shocking to most virologists and epidemiologists that airborne dust, rather than expiratory droplets, can carry influenza virus capable of infecting animals. Transmission via dust opens up whole new areas of investigation and has profound implications for how we interpret laboratory experiments as well as epidemiological investigations of outbreaks," said the study’s lead researcher William Ristenpart of the UC Davis Department of Chemical Engineering.

Researchers previously believed that airborne viruses like the influenza virus spread by several different routes, such as respiratory droplets from an infected person or via secondary objects like used tissues or door handles. However, very little is known about which routes are more important.

Dried influenza virus can transmit the infection through air

The experts at UC Davis in collaboration with the virologists at Mount Sinai said they demonstrated that infected guinea pigs heavily contaminate their fur and surrounding environment with virus and that "if these dust particulates become contaminated with influenza virus they can serve as aerosolized fomites that carry the virus to a susceptible guinea pig through the air."

They then sought to analyze whether tiny nonrespiratory particles could carry the virus between guinea pigs. For this they used an automated particle sizer that counted airborne particles. Their observations on uninfected guinea pigs showed that the animals gave off spikes of up to 1,000 particles per second while they moved around their cage. Surprisingly, they found that the guinea pigs’ gave off the particles at a much lower rate during normal breathing.

They found that immune but contaminated guinea pigs carried the virus on their fur and transmitted it through the air to other vulnerable animals. The study demonstrated that the virus didn’t have to come directly from the respiratory tract to be infectious.

"We conclude that airborne particulate matter from a non-respiratory source is able to transmit influenza virus through the air to a susceptible host," the researchers said.

They also tested whether microscopic fibers from an inanimate object could carry infectious viral particles. After treating paper facial tissues with the virus, they dried them out and then crumpled them in front of the automated particle sizer. They found that crumpling the paper tissues released up to 900 particles per second in a size range that could be inhaled. Particles from the contaminated paper tissues were able to infect cells.

"Dried influenza virus remains viable in the environment, on materials like paper tissues and on the bodies of living animals, long enough to be aerosolized on non-respiratory dust particles that can transmit the infection through the air to new mammalian hosts," said the researchers in their paper published in Nature Communications.