SARS-CoV-2 Lessons Learned May Evolve Understanding and Vocabulary Around Airborne-Related Transmission
Aerosol transmission is the major mode of transmission and key mitigation strategies include vaccines and wearing masks indoors when outside a person ’ s household bubble .”
By Kelly M . Pyrek
In the 2021 IDWeek presentation , “ Say It , Don ’ t
Spray It : Examining the Perspectives on Aerosol and Virus transmission : A Hospital Epidemiologist ’ s Standpoint ,” David Weber , MD , MPH , reviewed what is currently known about the transmission of SARS-CoV-2 , specifically that droplet ( short distances ) is the most important mode of transmission and that overwhelmingly , this transmission occurs indoors . Pre-symptomatic and asymptomatic transmission are important contributors to transmission . Direct contact plays a role and indirect contact via the contaminated environment is likely but not considered to be a significant mode of transmission . Airborne transmission over longer distances is likely but uncommon .
“ This disease is transmitted by aerosol route , meaning an infected person breathes , coughs , sneezes out infectious particles ,” Weber said . “ In general , that short distance of travel is the most important mode of transmission , although longer-distance transmission has also occurred when the uninfected person inhales them . Some of those particles can fall onto surfaces , and it is possible , potentially , that an uninfected person would touch a surface and then touch their nose or mouth and acquire disease that way . We know that SARS-CoV-2 can survive for minutes to hours on surfaces . Longer-range airborne transmission can occur under certain circumstances indoors with unmasked people and with directional airflow with poor ventilation . Aerosol transmission is the major mode of transmission and key mitigation strategies include vaccines and wearing masks indoors when outside a person ’ s household bubble .
In healthcare facilities , everyone should adhere to universal pandemic precautions , wearing a mask 100 percent of the time , eye protection in addition to masks for any contact with patients , and wearing an N95 respirator when dealing with known or suspected COVID-19 patients , as well as when performing aerosol-generating procedures .”
Weber reviewed the evidence for longer-distance aerosol transmission . “ We know that the expulsion of droplets can extend beyond 6 feet ,” he said . “ We also know that regarding SARS-CoV-2 , if you put contaminated air in a rotating drum during an experiment , it will last a long period of time , as studies have demonstrated substantial SARS-CoV-2 RNA and occasionally viable virus more than 6 feet of distance from a COVID patient .”
The challenge , Weber said , was that “ the survival of SARS-CoV-2 in a rotating drum is consistent with aerosol transmission but doesn ’ t demonstrate airborne transmission . It ’ s artificial , since there isn ’ t any settling or drying of the particles . Indication of SARS-CoV-2 RNA , which has been demonstrated outside of patient rooms , doesn ’ t mean that there was viable virus present , or that there was an infectious or viable dose of virus in the air . Now , there have been some recommendations to improve a room ’ s ventilation , and various disinfection systems , but those should not be implemented until studies demonstrate efficacy , just as we would wait for that evidence for any other infection prevention-related intervention that we want to implement . There have been recommendations for more ‘ natural ’ air , but this