With flu season approaching, it may be worth giving your house a thorough clean.
Although typically spread via coughs and sneezes, research suggests flu viruses may also travel through the air in dust.
Scientists from the University of California, Davis, “painted” a flu virus strain on the fur of guinea pigs that were immune to the pathogen.
Read more: When should you not ignore a cough?
The animals transmitted the virus to uninfected guinea pigs, despite not carrying it in their respiratory tract.
The scientists concluded flu viruses may therefore spread in the air via dust, fibres and microscopic particles.
The team state this has “obvious implications” for the coronavirus, however, they stressed it is unclear whether the same results would apply to other respiratory infections or even additional flu strains.
“It’s really shocking to most virologists and epidemiologists that airborne dust, rather than expiratory droplets, can carry influenza virus capable of infecting animals,” said study author Professor William Ristenpart.
“The implicit assumption is always that airborne transmission occurs because of respiratory droplets emitted by coughing, sneezing or talking.
“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.”
There are three types of flu viruses – A, B and C. Every year, one or two strains of type A – typically the most severe – circulate, as well as type B, which generally causes a less severe illness.
Each February, the World Health Organization (WHO) assesses the strains that are most likely to be circulating in the northern hemisphere over the following winter.
Based on this, the WHO recommends which flu strains vaccines should protect against.
The NHS advises at-risk patients get the jab before the UK’s flu season, which typically runs from December to March.
As well as spreading via coughs and sneezes, the viruses are known to survive on certain surfaces, like door handles or used tissues – known as fomites.
To better understand the different ways the virus may land on these objects, the scientists looked at whether tiny, non-respiratory particles they called “aerosolised fomites” could carry the pathogen between guinea pigs.
Animals that were immune to flu had the virus painted on their fur.
Using an automated sizer, the scientists found the guinea pigs gave off up to 1,000 virus particles per second as they moved around their cage.
These went on to infect other susceptible animals, according to results published in the journal Nature Communications.
Finally, the scientists tested whether microscopic fibres from an inanimate object could carry infectious viruses.
They exposed tissues to a flu virus, let them dry out and then crumpled the tissues in front of the automated particle sizer.
Crumpling the tissues released up to 900 particles per second, at a size that could be inhaled.
These virus-contaminated tissues were also capable of infecting cells in the laboratory, the results revealed.