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This is a summary of "Transmission Potential of SARS-CoV-2 in Viral Shedding Observed at the University of Nebraska Medical Center"


Is COVID-19 spread through airborne transmission and surfaces?

Pieces of the SARS-CoV-2 virus are detectable after breathing, using the toilet, and touching surfaces, but this study did not recover any infectious virus particles nor provide evidence of human-to-human spread of COVID-19 through small airborne particles or surfaces.

Key takeaways

Why is this important?

In order to design effective policies and procedures to prevent the spread of COVID-19, we need to know if it’s spread by droplets versus airborne transmission. The difference is that droplets are generally large and fall relatively quickly on the ground and objects nearby, and aerosolized particles (airborne transmission) happens with much smaller droplets that can hang in the air for a much longer time period.

If COVID-19 is spread by airborne transmission, much stricter restrictions need to be placed in order to protect the general public. This difference is important for indoors activities, especially in shared spaces with heavy breathing, like concerts, gyms or choirs. Surface transmission is also important to understand for policy making. For example, based on current research, the CDC does not believe that contaminated objects are a main source of infectious spread. Any evidence either supporting or refuting this would be very valuable to have.

Our take

During the course of this study the researchers at the University of Nebraska gathered samples from a small number of patients infected with COVID-19. Samples were taken from common objects (remote controls, phones, personal items, etc), surfaces (bathrooms, window ledge, air gratings), and air (both inside the patient’s room, as well as the hallway outside). Between 50-100% of each sample type showed viral genetic materials, meaning the presence of the virus or parts of the virus. Samples from patients’ rooms who had a higher fever did not show a higher level of virus. Air samples from patients who required hospital care (more severe symptoms) did not show a higher level of virus than air samples from the patients who had mild or no symptoms. The researchers were not able to use the virus samples obtained from objects or the air to infect cells in a laboratory setting.


The biggest strength of this study was that they tried to culture all of their samples to see if the virus could infect cells in a laboratory setting. The University of Nebraska’s Biocontainment and Quarantine units have the resources to perform this kind of study which most places cannot easily do.


It’s not clear from the paper if they had successfully cultured SARS-CoV-2 from a hallway air sample. The text suggests that they did not and Figure 2 suggests that they did. The difference between these two interpretations is huge, because if the hallway air sample was infectious, that suggests airborne transmission. They were unable to use any of the other samples to infect cells.

This paper was missing some important positive and negative controls. The infection of cells in a lab setting did not have a positive control - for example, asking a patient to provide a droplet sample and culturing that using the same methods. Because of how they did it, we have no idea if the samples were not infectious, or if they were not infectious because of how they were handled. The testing for the presence of genetic material did not have a negative control. This is important to show that there was no contamination or other errors.

What did the study do?

How was it reported?

The original paper is a preprint study. It has not been certified by peer review from other researchers, and information presented may be erroneous. Do not use it to guide clinical practice! Learn more →

Original Paper DOI10.1101/2020.03.23.20039446

Transmission Potential of SARS-CoV-2 in Viral Shedding Observed at the University of Nebraska Medical Center [PDF]

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