report, associate professor of pathology and microbiology at
UNMC and research director for Countering Weapons of Mass
Destruction at the National Strategic Research Institute. “This
ongoing work will continue to improve our understanding of
SARS-CoV-2 transmission and help identify ways to improve
safety in the care of patients with this disease.”
In this study by Santarpia, et al. (2020) the researchers
acknowledge that a 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
Understanding were collected in 11 isolation rooms
the modes of to examine viral shedding from isolated
individuals. While all individuals were
transmission of confirmed positive for SARS-CoV-2,
emerging infectious symptoms and viral shedding to the
15 environments varied considerably,”
disease is a key the researchers note.
They continue, “Many commonly
factor in protecting
used items, toilet facilities, and air
healthcare workers samples had evidence of viral contam-
and implementing ination, indicating that SARS-CoV-2 is
to the environment as expired
effective public shed
particles, during toileting, and through
health measures.” contact with fomites. Disease spreads
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.”
As the researchers emphasize, “Understanding the modes
of transmission of emerging infectious disease is a key factor
in protecting healthcare workers and implementing effective
public health measures. The lack of evidence on SARS-CoV-2
transmission dynamics has led to shifting isolation guidelines
between airborne and droplet isolation precautions by
the WHO, CDC and other public health authorities. Other
emerging coronaviruses (e.g. SARS and MERS) have been
suggested to have airborne transmission potential in addition
to more direct contact and droplet transmission. At least
one study suggests that MERS-CoV has the possibility of
transmission from mildly ill or asymptomatic individuals.
Surface samples taken in patient-care areas for MERS and
SARS have shown positive PCR results; however, experts
question the possibility of transmission through contact with
surfaces that have been contaminated by an infected person,
either by the direct contact of the infected person or the
settling of virus-laden particles onto the surface. Nonetheless,
coronaviruses have been implicated in nosocomial outbreaks
with reports of transmission related to environmental
contamination. Nosocomial transmission of SARS-CoV-2
has been reported, but the role of aerosol transmission and
environmental contamination remains unclear.”
The researchers found that overall, 76.5 percent of all
personal items sampled were determined to be positive for
SARS-CoV-2 by PCR. Of these samples, 81.3 percent of the
miscellaneous personal items, which included exercise equip-
ment, medical equipment (spirometer, pulse oximeter, nasal
cannula), personal computers, iPads and reading glasses),
26
were positive by PCR, with a mean concentration of 0.217
copies/µL. Cellular phones were 83.3 percent positive for
viral RNA and remote controls for in-room televisions were
64.7 percent percent positive. Samples of the toilets in the
room were 81 percent positive, with a mean concentration
of 0.252 copies/µL. Of all room surfaces sampled, 80.4
percent were positive for SARS-CoV-2 RNA. This included
75 percent of the bedside tables and bed rails indicating the
presence of viral RNA, as did 81.8 percent of the window
ledges sampled in each room. The floor beneath patients’
beds and the ventilation grates in the NBU were also sampled;
all five floor samples, as well as 4.35 of the 5 ventilation
grate samples tested positive by RT-PCR.”
Regarding air sampling, Santarpia, et al. (2020) found
that both personal air samplers from sampling personnel in
the NQU showed positive PCR results after 122 minutes of
sampling activity, and both air samplers from NBU sampling
indicated the presence of viral RNA after only 20 minutes of
sampling activity. The highest airborne concentrations were
recorded by personal samplers in NBU while a patient was
receiving oxygen through a nasal cannula. 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.
As the researchers note, “Taken together, these data
indicate significant environmental contamination in rooms
where 40 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. 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.”
They add, “Recent literature investigating human expired
aerosol indicates that a significant fraction of human expired
aerosol is less than 10 µm in diameter across all types of
activity (e.g. breathing, talking, and coughing) and that upper
respiratory illness increases production of aerosol particles
(less than 10 µm). 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. Further,
a recent study of SARS-CoV-2 in aerosol and deposited on
surfaces, indicates infectious aerosol may persist for several
hours and on surfaces for as long as two days. Despite
wide-spread environmental and limited SARS-CoV-2 aerosol
contamination associated with hospitalized and mildly ill
individuals, effective implementation of airborne isolation
precautions including N95 filtering facepiece respirators and
powered air purifying respirator use adequately protected
healthcare workers, in the NQU and NBU facilities, preventing
healthcare worker infections. Healthcare workers were
closely monitored and screened for COVID-19 suggesting
the value in implementing IPC protocols that maintain
april 2020 • www.healthcarehygienemagazine.com