Universal Masking in Hospitals in the Covid-19 Era
List of authors.- Michael Klompas, M.D., M.P.H.,
- Charles A. Morris, M.D., M.P.H.,
- Julia Sinclair, M.B.A.,
- Madelyn Pearson, D.N.P., R.N.,
- and Erica S. Shenoy, M.D., Ph.D.
As
the SARS-CoV-2 pandemic continues to explode, hospital systems are
scrambling to intensify their measures for protecting patients and
health care workers from the virus. An increasing number of frontline
providers are wondering whether this effort should include universal use
of masks by all health care workers. Universal masking is already
standard practice in Hong Kong, Singapore, and other parts of Asia and
has recently been adopted by a handful of U.S. hospitals.
We
know that wearing a mask outside health care facilities offers little,
if any, protection from infection. Public health authorities define a
significant exposure to Covid-19 as face-to-face contact within 6 feet
with a patient with symptomatic Covid-19 that is sustained for at least a
few minutes (and some say more than 10 minutes or even 30 minutes). The
chance of catching Covid-19 from a passing interaction in a public
space is therefore minimal. In many cases, the desire for widespread
masking is a reflexive reaction to anxiety over the pandemic.
The calculus may be different, however,
in health care settings. First and foremost, a mask is a core component
of the personal protective equipment (PPE) clinicians need when caring
for symptomatic patients with respiratory viral infections, in
conjunction with gown, gloves, and eye protection. Masking in this
context is already part of routine operations for most hospitals. What
is less clear is whether a mask offers any further protection in health
care settings in which the wearer has no direct interactions with
symptomatic patients. There are two scenarios in which there may be
possible benefits.
The first is during the care of a
patient with unrecognized Covid-19. A mask alone in this setting will
reduce risk only slightly, however, since it does not provide protection
from droplets that may enter the eyes or from fomites on the patient or
in the environment that providers may pick up on their hands and carry
to their mucous membranes (particularly given the concern that mask
wearers may have an increased tendency to touch their faces).
More
compelling is the possibility that wearing a mask may reduce the
likelihood of transmission from asymptomatic and minimally symptomatic
health care workers with Covid-19 to other providers and patients. This
concern increases as Covid-19 becomes more widespread in the community.
We face a constant risk that a health care worker with early infection
may bring the virus into our facilities and transmit it to others.
Transmission from people with asymptomatic infection has been well
documented, although it is unclear to what extent such transmission
contributes to the overall spread of infection.1-3
More
insidious may be the health care worker who comes to work with mild and
ambiguous symptoms, such as fatigue or muscle aches, or a scratchy
throat and mild nasal congestion, that they attribute to working long
hours or stress or seasonal allergies, rather than recognizing that they
may have early or mild Covid-19. In our hospitals, we have already seen
a number of instances in which staff members either came to work well
but developed symptoms of Covid-19 partway through their shifts or
worked with mild and ambiguous symptoms that were subsequently diagnosed
as Covid-19. These cases have led to large numbers of our patients and
staff members being exposed to the virus and a handful of potentially
linked infections in health care workers. Masking all providers might
limit transmission from these sources by stopping asymptomatic and
minimally symptomatic health care workers from spreading virus-laden
oral and nasal droplets.
What is clear, however, is
that universal masking alone is not a panacea. A mask will not protect
providers caring for a patient with active Covid-19 if it’s not
accompanied by meticulous hand hygiene, eye protection, gloves, and a
gown. A mask alone will not prevent health care workers with early
Covid-19 from contaminating their hands and spreading the virus to
patients and colleagues. Focusing on universal masking alone may,
paradoxically, lead to more transmission of Covid-19 if it diverts
attention from implementing more fundamental infection-control measures.
Such
measures include vigorous screening of all patients coming to a
facility for symptoms of Covid-19 and immediately getting them masked
and into a room; early implementation of contact and droplet
precautions, including eye protection, for all symptomatic patients and
erring on the side of caution when in doubt; rescreening all admitted
patients daily for signs and symptoms of Covid-19 in case an infection
was incubating on admission or they were exposed to the virus in the
hospital; having a low threshold for testing patients with even mild
symptoms potentially attributable to a viral respiratory infection (this
includes patients with pneumonia, given that a third or more of
pneumonias are caused by viruses rather than bacteria); requiring
employees to attest that they have no symptoms before starting work each
day; being attentive to physical distancing between staff members in
all settings (including potentially neglected settings such as
elevators, hospital shuttle buses, clinical rounds, and work rooms);
restricting and screening visitors; and increasing the frequency and
reliability of hand hygiene.
The extent of marginal
benefit of universal masking over and above these foundational measures
is debatable. It depends on the prevalence of health care workers with
asymptomatic and minimally symptomatic infections as well as the
relative contribution of this population to the spread of infection. It
is informative, in this regard, that the prevalence of Covid-19 among
asymptomatic evacuees from Wuhan during the height of the epidemic there
was only 1 to 3%.4,5
Modelers assessing the spread of infection in Wuhan have noted the
importance of undiagnosed infections in fueling the spread of Covid-19
while also acknowledging that the transmission risk from this population
is likely to be lower than the risk of spread from symptomatic
patients.3
And then the potential benefits of universal masking need to be
balanced against the future risk of running out of masks and thereby
exposing clinicians to the much greater risk of caring for symptomatic
patients without a mask. Providing each health care worker with one mask
per day for extended use, however, may paradoxically improve inventory
control by reducing one-time uses and facilitating centralized workflows
for allocating masks without risk assessments at the
individual-employee level.
There may be additional
benefits to broad masking policies that extend beyond their technical
contribution to reducing pathogen transmission. Masks are visible
reminders of an otherwise invisible yet widely prevalent pathogen and
may remind people of the importance of social distancing and other
infection-control measures.
It is also clear that
masks serve symbolic roles. Masks are not only tools, they are also
talismans that may help increase health care workers’ perceived sense of
safety, well-being, and trust in their hospitals. Although such
reactions may not be strictly logical, we are all subject to fear and
anxiety, especially during times of crisis. One might argue that fear
and anxiety are better countered with data and education than with a
marginally beneficial mask, particularly in light of the worldwide mask
shortage, but it is difficult to get clinicians to hear this message in
the heat of the current crisis. Expanded masking protocols’ greatest
contribution may be to reduce the transmission of anxiety, over and
above whatever role they may play in reducing transmission of Covid-19.
The potential value of universal masking in giving health care workers
the confidence to absorb and implement the more foundational
infection-prevention practices described above may be its greatest
contribution.
Disclosure forms provided by the authors are available at NEJM.org.
This article was published on April 1, 2020, at NEJM.org.
Author Affiliations
From
the Department of Population Medicine, Harvard Medical School and
Harvard Pilgrim Health Care Institute (M.K.), Brigham and Women’s
Hospital (M.K., C.A.M., J.S., M.P.), Harvard Medical School (M.K.,
C.A.M., E.S.S.), and the Infection Control Unit and Division of
Infectious Diseases, Massachusetts General Hospital (E.S.S.) — all in
Boston.
Supplementary Material
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References (5)
- 1. Rothe C, Schunk M, Sothmann P, et al. Transmission of 2019-nCoV infection from an asymptomatic contact in Germany. N Engl J Med 2020;382:970-971.
- 2. Bai Y, Yao L, Wei T, et al. Presumed asymptomatic carrier transmission of COVID-19. JAMA 2020 February 21 (Epub ahead of print).
- 3. Li R, Pei S, Chen B, et al. Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2). Science 2020 March 16 (Epub ahead of print).
- 4. Hoehl S, Rabenau H, Berger A, et al. Evidence of SARS-CoV-2 infection in returning travelers from Wuhan, China. N Engl J Med 2020;382:1278-1280.
- 5. Ng O-T, Marimuthu K, Chia P-Y, et al. SARS-CoV-2 infection among travelers returning from Wuhan, China. N Engl J Med 2020;382:1476-1478.
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