Airborne transmission of SARS-CoV-2 is more serious: study

The study, published in Nature Communications, defines how the different routes of exposure to the virus relate to the severity of the disease. It details the efficiency of airborne transmission between hamsters and examines how the virus replicates and causes disease throughout the respiratory system.

“Transmission of the virus via passive vectors – exposure through contact with a contaminated surface – is significantly less efficient than airborne transmission but does occur,” the study said. Scientists from the National Institute of Allergy and Infectious Diseases at the NIH conducted the experiments at Rocky Mountain Laboratories in Hamilton, Montana.

To study how different routes of exposure affected the development of the disease, scientists exposed hamsters to SARS-CoV-2 via aerosols and passive vectors. For aerosol exposure, the scientists used equipment that controlled the size of droplets loaded with viruses. For exposure to fomites, they placed a dish contaminated with SARS-CoV-2 in the cages of the animals.

Scientists found that exposure to aerosols directly deposited SARS-CoV-2 deep in the lungs, while exposure to fomites caused the virus to replicate initially in the nose. Regardless of the route of exposure, the animals showed replication of SARS-CoV-2 in the lungs, but lung damage was more severe in animals exposed to the aerosols.

A second part of the study compared the transmission of the virus from one animal to another by air and in contaminated cages (fomites). Airborne droplets are a key transmission route for SARS-CoV-2, according to the study.

A further experiment, using circulating air from infected animals to uninfected animals, confirmed that reversing the airflow from uninfected animals to infected animals significantly reduced the efficiency of transmission.

The findings support public health directions focused on interventions to reduce indoor airborne transmission. These efforts include masking, increasing air filtration and social distancing, as well as regular hand washing and disinfection of surfaces, especially in clinical settings.