NIAID CEIRS | Research Publication Commentary
As the COVID-19 pandemic continues, it becomes more important to determine the modes of transmission of the SARS-CoV-2 virus. Respiratory viruses can spread through direct and indirect contact, and though respiratory droplets or aerosols spread. Aerosol spread is spread of infectious disease via respiratory droplets in the air. Respiratory droplets are larger droplets generated by an ill person an animal that fall out of the air more quickly than smaller aerosol droplets, which can spread further away from the infected individual to infect others. Understanding whether SARS-CoV-2 can spread through the air will enable public health experts to identify the appropriate control measures to reduce the spread of the outbreak. In a study published in Nature Communications, CEIRS investigators showed that SARS-CoV-2 is transmitted between ferrets through direct contact and via respiratory droplets and aerosols between ferrets.
To determine if SARS-CoV-2 can transmit through the air between ferrets, investigators inoculated ferrets with the virus and placed them in a cage. Uninfected ferrets were placed in cages 10 cm away, separated by steel grids. In this way, the virus could only be transmitted through the air. Uninfected ferrets were also placed in the cage with the infected ferrets to test direct contact transmission of the virus. Throat, nasal, and rectal swabs were collected from ferrets and tested for SARS-CoV-2 detection using RT-qPCR and virus titration.
Through this experiment, investigators showed that the SARS-CoV-2 was transmitted to the direct contact ferrets between 1 and 3 days after exposure. SARS-CoV-2 was also transmitted to the indirect ferrets through the air between 3 and 7 days after exposure. Viral RNA was detected in both ferret groups for at least two weeks, in shedding patterns similar to the inoculated ferrets.
This experiment shows that SARS-CoV-2 can be spread through the air between ferrets and result in infection. The investigators acknowledge that their experiment did not determine if the virus spread through the air via respiratory droplets or aerosols, but their study provides an important piece of evidence that airborne transmission of the virus is possible. Further experiments will be needed to determine the full extent of aerosol transmission of SARS-CoV-2, but this publication provides important information for public health officials implementing social distancing regulations and for hospitals’ infection control practices.