Transmission Potential of SARS-CoV-2 in Viral Shedding Observed at the University of Nebraska Medical Center
Authors: Joshua L. Santarpia, Danielle N. Rivera, et.al.
"Lack of evidence on SARS-CoV-2 transmission dynamics has led to shifting isolation guidelines between airborne and droplet isolation precautions.
During the initial isolation of 13 individuals confirmed positive with COVID-19 infection, air and surface samples were collected in eleven isolation rooms to examine viral shedding from isolated individuals.
While all individuals were confirmed positive for SARS-CoV-2, symptoms and viral shedding to the environment varied considerably.
Many commonly used items, toilet facilities, and air samples had evidence of viral contamination, indicating that SARS-CoV-2 is shed to the environment as expired particles, during toileting, and through contact with fomites.
Disease spread through both direct (droplet and person-to-person) as well as indirect contact (contaminated objects and airborne transmission) are indicated, supporting the use of airborne isolation precautions.
Three types of samples were taken during this survey: surface samples, high volume air samples, and low volume personal air samples. The surface samples fell into three general categories of location: common room surfaces, personal items, and toilets.
Personal items were those items considered to be handled routinely by individuals in isolation and included: cellular phones, exercise equipment, television remotes, and medical equipment. Room surfaces were areas such as ventilation grates, tabletops, and window ledges.
Toilet samples were taken to evaluate the potential for viral shedding during toileting.
Air samples were collected both in isolation rooms and in the hallways of the NBU and NQU during sampling activities. Air samples were collected in the room while patients were present. Air samples were taken in the hallways during sampling activities and samplers were placed on the floor adjacent to rooms where sampling activities were taking place.
Overall, 76.5% of all personal items sampled were determined to be positive for SARS-CoV-2 by PCR (Figure 1B and 2A). Of these samples, 81.3% of the miscellaneous personal items, which included exercise equipment, medical equipment (spirometer, pulse oximeter, nasal cannula), personal computers, iPads and reading glasses, were positive by PCR, with a mean concentration of 0.217 copies/”L.
Cellular phones were 83.3% positive for viral RNA (0.172 copies/”L mean concentration) and remote controls for in-room televisions were 64.7% percent positive (mean of 0.230 copies/”L).
Samples of the toilets in the room were 81.0% positive, with a mean concentration of 0.252 copies/”L.
Of all room surfaces sampled (Figure 1B and 2A), 80.4% were positive for SARS-CoV-2 RNA. This included 75.0% of the bedside tables and bed rails indicating the presence of viral RNA (mean concentration 0.263 copies/”L), as did 81.8% of the window ledges (mean concentration 0.219 copies/”L) sampled in each room.
The floor beneath patientsâ beds and the ventilation grates in the NBU were also sampled. All five floor samples, as well as 4 of the 5 ventilation grate samples tested positive by RT-PCR, with mean concentrations of 0.447 and 0.819 copies/”L, respectively.
Samples taken outside the rooms in the hallways were 66.7% positive (Figure 1B and 2B), with a mean concentration of 2.59 copies/L of air. Both personal air samplers from sampling personnel in the NQU showed positive PCR results after 122 minutes of sampling activity (Figure 2B), and both air samplers from NBU sampling indicated the presence of viral RNA after only 20 minutes of sampling activity (Figure 2B).
The highest airborne concentrations were recorded by personal samplers in NBU while a patient was receiving oxygen through a nasal cannula (19.17 and 48.21 copies/L). Neither individuals in the NQU or patients in the NBU were observed to cough while sampling personnel were in the room wearing samplers during these events.
Taken together, these data indicate significant environmental contamination in rooms where patients infected with SARS-CoV-2 are housed and cared for, regardless of the degree of symptoms or acuity of illness.
Contamination exists in all types of samples: high and low-volume air samples, as well as surface samples including personal items, room surfaces, and toilets.
Samples of patient toilets that tested positive for viral RNA are consistent with other reports of
viral shedding in stool (14).
The presence of contamination on personal items is also reasonably expected, particularly those items that are routinely handled by individuals in isolation, such as cell phones and remote controls, as well as medical equipment that is in near constant contact with the patient.
Recent literature investigating human expired aerosol indicates that a significant fraction of human expired aerosol is less than 10 ”m in diameter across all types of activity (e.g. breathing, talking, and coughing; 18) and that upper respiratory illness increases production of aerosol particles (less than 10 ”m; 19).
Taken together these results suggest that virus expelled from infected individuals, including from those who are only mildly ill, may be transported by aerosol processes in their local environment, potentially even in the absence of cough or aerosol generating procedures. "