World Health Organisation (WHO)
advice-for-workplace-clean
1
19 March 2020
Getting your workplace ready for COVID-19
How COVID-19 spreads
When someone who has COVID-19 coughs or exhales they release droplets of infected fluid. Most of these
droplets fall on nearby surfaces and objects, such as desks, tables or telephones. People could catch
COVID-19 by touching contaminated surfaces or objects, and then touching their eyes, nose, or mouth. If
they are standing within 1 meter of a person with COVID-19 they can catch it by breathing in droplets
coughed out or exhaled by them. In other words, COVID-19 spreads in a similar way to flu. Most persons
infected with COVID-19 experience mild symptoms and recover. However, some experience more serious
illness and may require hospital care. Risk of serious illness rises with age: people over 40 seem to be
more vulnerable than those under 40. People with weakened immune systems and people with conditions
such as diabetes, heart and lung disease are also more vulnerable to serious illness.
This document gives advice on:
1. Simple ways to prevent the spread of COVID-19 in your workplace
2. How to manage COVID-19 risks when organizing meetings and events
3. Things to consider when you and your employees travel
4. Getting your workplace ready in case COVID-19 arrives in your community.
1. Simple ways to prevent the spread of COVID-19 in your workplace
The low-cost measures below will help prevent the spread of infections in your workplace, such as colds,
flu and stomach bugs, and protect your customers, contractors, and employees.
Employers should start doing these things now, even if COVID-19 has not arrived in the communities
where they operate. These measures can reduce working days lost due to illness and stop or slow the
spread of COVID-19 if it arrives at one of your workplaces.
• Make sure your workplaces are clean and hygienic
– Surfaces (e.g. desks and tables) and objects (e.g. telephones, keyboards) need to be wiped
with disinfectant regularly
– Why? Because contamination on surfaces touched by employees and customers is one of
the main ways that COVID-19 spreads.
2
• Promote regular and thorough hand-washing by employees, contractors, and customers
– Put sanitizing hand rub dispensers in prominent places around the workplace. Make sure
these dispensers are regularly refilled
– Display posters promoting hand-washing – ask your local public health authority for these
or consult
– Combine with other communication measures such as offering guidance from
occupational health and safety officers, briefings at meetings, and information on intranet
sites to promote hand-washing
– Make sure that staff, contractors, and customers have access to places where they can
wash their hands with soap and water
– Why? Because washing kills the virus on your hands and prevents the spread of COVID-
19.
• Promote good respiratory hygiene in the workplace
– Display posters promoting respiratory hygiene. Combine this with other communication
measures such as guidance from occupational health and safety officers, briefing at
meetings, and information on the intranet, etc.
– Ensure that face masks
1
or paper tissues are available at your workplaces, for those who
develop a runny nose or cough at work, along with closed bins for hygienically disposing
of them
– Why? Because good respiratory hygiene prevents the spread of COVID-19.
• Advise employees and contractors to consult national travel advice before going on business trips.
• Brief your employees, contractors, and customers that if COVID-19 starts spreading in your
community anyone with even a mild cough or low-grade fever (37.3 C or more) needs to stay at
home. They should also stay home (or work from home) if they have had to take simple
medications, such as paracetamol/acetaminophen, ibuprofen or aspirin, which may mask
symptoms of infection
– Keep promoting the message that people need to stay at home even if they have only
mild symptoms of COVID-19
– Display posters with this message in your workplaces. Combine this with other
communication channels commonly used in your organization or business
1
Ordinary medical masks rather than N95 masks
3
– Your occupational health services, local public health authority, or other partners may
have developed campaign materials to promote this message
– Make clear to employees that they will be able to count this time off as sick leave
2. How to manage COVID-19 risk when organizing meetings and events
Why do employers and organizers need to think about COVID-19?
Organizers of meetings and events need to think about the potential risk from COVID-19 because:
• There is a risk that people attending your meeting or event might unwittingly bring the COVID-19
virus to the meeting. Others might be unknowingly exposed to COVID-19.
• Although COVID-19 is a mild disease for most people, it can make some very ill. Around 1 in every
5 people who catch COVID-19 needs hospital treatment.
Key considerations to prevent or reduce COVID-19 risks
BEFORE the meeting or event
• Check the advice from the authorities in the community where you plan to hold the meeting or
event. Follow their advice.
• Develop and agree a preparedness plan to prevent infection at your meeting or event.
– Consider whether a face-to-face meeting or event is needed. Could it be replaced by a
teleconference or online event?
– Could the meeting or event be scaled down so that fewer people attend?
– Verify information and communication channels in advance with key partners such as
public health and health care authorities.
– Pre-order sufficient supplies and materials, including tissues and hand sanitizer for all
participants. Have surgical masks available to offer anyone who develops respiratory
symptoms.
– Actively monitor where COVID-19 is circulating. Advise participants in advance that if they
have any symptoms or feel unwell, they should not attend.
– Make sure all organizers, participants, caterers, and visitors at the event provide contact
details: mobile telephone number, email, and address where they are staying. State
4
clearly that their details will be shared with local public health authorities if any
participant becomes ill with a suspected infectious disease. Anyone who does not agree
to this condition cannot attend the event or meeting.
• Develop and agree a response plan in case someone at the meeting becomes ill with symptoms
of COVID-19 (dry cough, fever, malaise). This plan should include at least:
– Identify a room or area where someone who is feeling unwell or has symptoms can be
safely isolated
– Have a plan for how they can be safely transferred from there to a health facility.
– Know what to do if a meeting participant, staff member, or service provider tests positive
for COVID-19 during or just after the meeting
– Agree the plan in advance with your partner health care provider or health department.
DURING the meeting or event
• Provide information or a briefing, preferably both orally and in writing, on COVID-19 and the
measures that organizers are taking to make this event safe for participants.
– Build trust. For example, as an icebreaker, practice ways to say hello without touching.
– Encourage regular hand-washing or use of an alcohol rub by all participants at the meeting
or event.
– Encourage participants to cover their face with the bend of their elbow or a tissue if they
cough or sneeze. Supply tissues and closed bins for disposal.
– Provide contact details or a health hotline number that participants can call for advice or
to give information.
• Display dispensers of alcohol-based hand rub prominently around the venue.
• If there is space, arrange seats so that participants are at least 1 meter apart.
• Open windows and doors whenever possible to make sure the venue is well ventilated.
• If anyone who starts to feel unwell, follow your preparedness plan or call your hotline.
o Depending on the situation in your area, or recent travel of the participant, place the
person in the isolation room. Offer the person a mask so they can get home safely, if
appropriate, or to a designated assessment facility.
• Thank all participants for their cooperation with the provisions in place.
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AFTER the meeting
1. Retain the names and contact details of all participants for at least one month. This will help public
health authorities trace people who may have been exposed to COVID-19 if one or more
participants become ill shortly after the event.
2. If someone at the meeting or event was isolated as a suspected COVID-19 case, the organizer
should inform participants. They should be advised to monitor themselves for symptoms for 14
days and take their temperature twice a day.
3. If they develop even a mild cough or low-grade fever (i.e. a temperature of 37.3 C or more) they
should stay at home and self-isolate. This means avoiding close contact (less than 1 meter) with
other people, including family members. They should also call their health care provider or the
local public health department, giving them details of their recent travel and symptoms.
4. Thank all the participants for their cooperation with the provisions in place.
6
3. Things to consider when you and your employees travel
• Before traveling
– Make sure your organization and its employees have the latest information on areas
where
COVID-19
is
spreading.
You
can
find
this
at
https://www.who.int/emergencies/diseases/novel-coronavirus-2019/situation-reports/.
– Based on the latest information, your organization should assess the benefits and risks
related to upcoming travel plans.
– Avoid sending employees who may be at higher risk of serious illness (e.g. older
employees and those with medical conditions such as diabetes, heart and lung disease)
to areas where COVID-19 is spreading.
– Make sure all persons travelling to locations reporting COVID-19 are briefed by a qualified
professional (e.g. staff health services, health care provider or local public health partner)
– Consider issuing employees who are about to travel with small bottles of alcohol-based
hand rub. This can facilitate regular hand-washing.
• While traveling:
– Encourage employees to wash their hands regularly and stay at least 1 m away from
people who are coughing or sneezing.
– Ensure employees know what to do and whom to contact if they feel ill while traveling.
– Ensure that your employees comply with instructions from local authorities and any local
restrictions on travel, movement, or large gatherings where they are travelling. .
• When you or your employees return from traveling:
– Employees who have returned from an area where COVID-19 is spreading should monitor
themselves for symptoms for 14 days and take their temperature twice a day.
– If they develop even a mild cough or low-grade fever (i.e. a temperature of 37.3 C or
more) they should stay at home and self-isolate. This means avoiding close contact (less
than 1 m) with other people, including family members. They should also call their health
care provider or the local public health department, giving them details of their recent
travel and symptoms.
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4. Getting your workplace ready in case COVID-19 arrives in your community
• Develop a plan for what to do if someone becomes ill with suspected COVID-19 at one of your
workplaces
– The plan should cover putting the ill person in a room or area where they are isolated
from others in the workplace, limiting the number of people who have contact with the
sick person, and contacting the local health authorities.
– Consider how to identify persons who may be at risk, and support them, without inviting
stigma and discrimination. This could include persons who have recently travelled to an
area reporting cases, or other personnel who have conditions that put them at higher risk
of serious illness (e.g. diabetes, heart and lung disease, older age).
– Tell your local public health authority you are developing the plan and seek their input.
• Promote regular teleworking across your organization. If there is an outbreak of COVID-19 in your
community the health authorities may advise people to avoid public transport and crowded
places. Teleworking will help your business keep operating while your employees stay safe.
• Develop a contingency and business continuity plan for an outbreak in the communities where
your business operates
– The plan will help prepare your organization for the possibility of an outbreak of COVID-
19 in its workplaces or community. It may also be valid for other health emergencies.
– The plan should address how to keep your business running even if a significant number
of employees, contractors and suppliers cannot come to your place of business, either
due to local restrictions on travel or because they are ill.
– Communicate to your employees and contractors about the plan and make sure they are
aware of what they need to do, or not do, under the plan. Emphasize key points such as
the importance of staying away from work even if they have only mild symptoms or have
had to take simple medications (e.g. paracetamol, ibuprofen) that may mask the
symptoms.
– Be sure your plan addresses the mental health and social consequences of a case of
COVID-19 in the workplace or in the community and offer information and support.
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– For small and medium-sized businesses without in-house staff health and welfare
support, develop partnerships and plans with your local health and social service
providers in advance of any emergency.
– Your local or national public health authority may be able to offer support and guidance
in developing your plan.
Remember:
Now is the time to prepare for COVID-19. Simple precautions and planning can make a big difference.
Action now will help protect your employees and your business.
How to stay informed:
Find the latest information from WHO on where COVID-19 is spreading:
https://www.who.int/emergencies/diseases/novel-coronavirus-2019/situation-reports/
Advice and guidance from WHO on COVID-19
https://www.who.int/emergencies/diseases/novel-coronavirus-2019
How to
put on, use,
take off and dispose
of a mask
Cover mouth and nose with mask
and make sure there are no gaps
between your face and the mask
Avoid touching the mask while using
it; if you do, clean your hands with
alcohol-based hand rub or soap and
water
To remove the mask: remove it from
behind (do not touch the front of
mask); discard immediately in a
closed bin; wash hands with alcohol-
based hand rub or soap and water
2
Replace the mask with a new one as
soon as it is damp and do not re-use
single-use masks
3
4
1
Before putting on a mask, wash
hands with alcohol-based hand rub
or soap and water
When to use a mask
Wear a mask if you are
coughing or sneezing
If you wear a mask then you
must know how to use it
and dispose of it properly
2
4
Masks are effective only
when used in combination
with frequent hand-washing
with alcohol-based hand
rub or soap and water
3
1
If you are healthy, you only
need to wear a mask if you
are taking care of a person
with suspected 2019-nCoV
infection
-
1-
Advice on the use of masks in the context of COVID-19
Interim guidance
6 April 2020
Background
This document provides advice on the use of masks in
communities, during home care, and in health care settings in
areas that have reported cases of COVID-19. It is intended for
individuals in the community, public health and infection
prevention and control (IPC) professionals, health care
managers, health care workers (HCWs), and community
health workers. It will be revised as more data become
available.
Current information suggests that the two main routes of
transmission of the COVID-19 virus are respiratory droplets
and contact. Respiratory droplets are generated when an
infected person coughs or sneezes. Any person who is in close
contact (within 1 m) with someone who has respiratory
symptoms (coughing, sneezing) is at risk of being exposed to
potentially infective respiratory droplets. Droplets may also
land on surfaces where the virus could remain viable; thus,
the immediate environment of an infected individual can
serve as a source of transmission (contact transmission).
1
WHO has recently summarized reports of transmission of the
COVID-19 virus and provided a brief overview of current
evidence on transmission from symptomatic, pre-
symptomatic, and asymptomatic
people infected with
COVID-19 (full details are provided in WHO COVID-19
Situation report 73).
2
Current evidence suggests that most disease is transmitted by
symptomatic laboratory confirmed cases. The incubation
period for COVID-19, which is the time between exposure to
the virus and symptom onset, is on average 5-6 days, but can
be as long as 14 days. During this period, also known as the
“pre-symptomatic” period, some infected persons can be
contagious and therefore transmit the virus to others.
3-8
In a
small number of reports, pre-symptomatic transmission has
been documented through contact tracing efforts and
enhanced investigation of clusters of confirmed cases.
3-8
This
is supported by data suggesting that some people can test
positive for COVID-19 from 1-3 days before they develop
symptoms.
9,10
Thus, it is possible that people infected with COVID-19 could
transmit the virus before symptoms develop. It is important
to recognize that pre-symptomatic transmission still requires
the virus to be spread via infectious droplets or through
a
An asymptomatic laboratory-confirmed case is a person infected with
COVID-19 who does not develop symptoms. Asymptomatic transmission
refers to transmission of the virus from a person, who does not develop
touching contaminated surfaces. WHO regularly monitors all
emerging evidence about this critical topic and will provide
updates as more information becomes available.
In this document medical masks are defined as surgical or
procedure masks that are flat or pleated (some are shaped like
cups); they are affixed to the head with straps. They are tested
according to a set of standardized test methods (ASTM F2100,
EN 14683, or equivalent) that aim to balance high filtration,
adequate breathability and optionally, fluid penetration
resistance. This document does not focus on respirators; for
guidance on use of respirators see IPC guidance during health
care when COVID-19 infection is suspected.
11
Wearing a medical mask is one of the prevention measures
that can limit the spread of certain respiratory viral diseases,
including COVID-19.
However, the use of a mask alone is
insufficient to provide an adequate level of protection, and
other measures should also be adopted. Whether or not
masks are used, maximum compliance with hand hygiene and
other IPC measures is critical to prevent human-to-human
transmission of COVID-19. WHO has developed guidance on
IPC strategies for home care
12
and health care settings
11
for
use when COVID-19 is suspected.
Community settings
Studies of influenza, influenza-like illness, and human
coronaviruses provide evidence that the use of a medical
mask can prevent the spread of infectious droplets from an
infected person to someone else and potential contamination
of the environment by these droplets.
13
There is limited
evidence that wearing a medical mask by healthy individuals
in the households or among contacts of a sick patient, or
among attendees of mass gatherings may be beneficial as a
preventive measure.
14-23
However, there is currently no
evidence that wearing a mask (whether medical or other types)
by healthy persons in the wider community setting, including
universal community masking, can prevent them from
infection with respiratory viruses, including COVID-19.
Medical masks should be reserved for health care workers.
The use of medical masks in the community may create a
false sense of security, with neglect of other essential
measures, such as hand hygiene practices and physical
distancing, and may lead to touching the face under the masks
and under the eyes, result in unnecessary costs, and take
symptoms. The true extent of asymptomatic infections will be determined
from serologic studies.
Advice on the use of masks in the context of COVID-19: interim guidance
-
2-
masks away from those in health care who need them most,
especially when masks are in short supply.
Persons with symptoms should:
•
wear a medical mask, self-isolate, and seek medical
advice as soon as they start to feel unwell. Symptoms can
include fever, fatigue, cough, sore throat, and difficulty
breathing. It is important to note that early symptoms for
some people infected with COVID-19 may be very mild;
•
follow instructions on how to put on, take off, and
dispose of medical masks;
•
follow all additional preventive measures, in particular,
hand hygiene and maintaining physical distance from
other persons.
All persons should:
•
avoid groups of people and enclosed, crowded spaces;
•
maintain physical distance of at least 1 m from other
persons, in particular from those with respiratory
symptoms (e.g., coughing, sneezing);
•
perform hand hygiene frequently, using an alcohol-based
hand rub if hands are not visibly dirty or soap and water
when hands are visibly dirty;
•
cover their nose and mouth with a bent elbow or paper
tissue when coughing or sneezing, dispose of the tissue
immediately after use, and perform hand hygiene;
•
refrain from touching their mouth, nose, and eyes.
In some countries masks are worn in accordance with local
customs or in accordance with advice by national authorities
in the context of COVID-19. In these situations, best practices
should be followed about how to wear, remove, and dispose
of them, and for hand hygiene after removal.
Advice to decision makers on the use of masks for healthy
people in community settings
As described above, the wide use of masks by healthy
people in the community setting is not supported by current
evidence and carries uncertainties and critical risks. WHO
offers the following advice to decision makers so they apply
a risk-based approach.
Decisions makers should consider the following:
1.
Purpose of mask use: the rationale and reason for mask
use should be clear– whether it is to be used for source
control (used by infected persons) or prevention of
COVID-19 (used by healthy persons)
2. Risk of
exposure to the COVID-19 virus in the local
context:
The population: current epidemiology about how
widely the virus is circulating (e.g., clusters of
cases versus community transmission), as well as
local surveillance and testing capacity (e.g., contact
tracing and follow up, ability to carry out testing).
The individual: working in close contact with
public (e.g., community health worker, cashier)
3.
Vulnerability of the person/population to develop
severe disease or be at higher risk of death, e.g. people
with comorbidities, such as cardiovascular disease or
diabetes mellitus, and older people
4.
Setting in which the population lives in terms of
population density, the ability to carry out physical
distancing (e.g. on a crowded bus), and risk of rapid
spread (e.g. closed settings, slums, camps/camp-like
settings).
5. Feasibility: availability and costs of the mask, and
tolerability by individuals
6.
Type of mask: medical mask versus nonmedical mask
(see below)
In addition to these factors, potential advantages of the use
of mask by healthy people in the community setting include
reducing potential exposure risk from infected person during
the “pre-symptomatic” period and stigmatization of
individuals wearing mask for source control.
However, the following potential risks should be carefully
taken into account in any decision-making process:
•
self-contamination that can occur by touching and
reusing contaminated mask
•
depending on type of mask used, potential breathing
difficulties
•
false sense of security, leading to potentially less
adherence to other preventive measures such as physical
distancing and hand hygiene
•
diversion of mask supplies and consequent shortage of
mask for health care workers
•
diversion of resources from effective public health
measures, such as hand hygiene
Whatever approach is taken, it is important to develop a
strong communication strategy to explain to the population
the circumstances, criteria, and reasons for decisions. The
population should receive clear instructions on what masks
to wear, when and how (see mask management section), and
on the importance of continuing to strictly follow all other
IPC measures (e.g., hand hygiene, physical distancing, and
others).
Type of Mask
WHO stresses that it is critical that medical masks and
respirators be prioritized for health care workers.
The use of masks made of other materials (e.g., cotton
fabric), also known as nonmedical masks, in the community
setting has not been well evaluated. There is no current
evidence to make a recommendation for or against their use
in this setting.
WHO is collaborating with research and development
partners to better understand the effectiveness and efficiency
of nonmedical masks. WHO is also strongly encouraging
countries that issue recommendations for the use of masks in
healthy people in the community to conduct research on this
critical topic. WHO will update its guidance when new
evidence becomes available.
Advice on the use of masks in the context of COVID-19: interim guidance
-
3-
In the interim, decision makers may be moving ahead with
advising the use of nonmedical masks. Where this is the
case, the following features related to nonmedical masks
should be taken into consideration:
•
Numbers of layers of fabric/tissue
•
Breathability of material used
•
Water repellence/hydrophobic qualities
•
Shape of mask
•
Fit of mask
Home care
For COVID-19 patients with mild illness, hospitalization may
not be required. All patients cared for outside hospital (i.e. at
home or non-traditional settings) should be instructed to
follow local/regional public health protocols for home
isolation and return to designated COVID-19 hospital if they
develop any worsening of illness.
7
Home care may also be considered when inpatient care is
unavailable or unsafe (e.g. capacity is limited, and resources
are unable to meet the demand for health care services).
Specific IPC guidance for home care should be followed.
3
Persons with suspected COVID-19 or mild symptoms
should:
•
Self-isolate if isolation in a medical facility is not
indicated or not possible
•
Perform hand hygiene frequently, using an alcohol-based
hand rub if hands are not visibly dirty or soap and water
when hands are visibly dirty;
•
Keep a distance of at least 1 m from other people;
•
Wear a medical mask as much as possible; the mask
should be changed at least once daily. Persons who
cannot tolerate a medical mask should rigorously apply
respiratory hygiene (i.e. cover mouth and nose with a
disposable paper tissue when coughing or sneezing and
dispose of it immediately after use or use a bent elbow
procedure and then perform hand hygiene.)
•
Avoid contaminating surfaces with saliva, phlegm, or
respiratory secretions.
•
Improve airflow and ventilation in their living space by
opening windows and doors as much as possible.
Caregivers or those sharing living space with persons
suspected of COVID-19 or with mild symptoms should:
•
Perform hand hygiene frequently, using an alcohol-based
hand rub if hands are not visibly dirty or soap and water
when hands are visibly dirty;
•
Keep a distance of at least 1 meter from the affected
person when possible;
•
Wear a medical mask when in the same room as the
affected person;
•
Dispose of any material contaminated with respiratory
secretions (disposable tissues) immediately after use and
then perform hand hygiene.
•
Improve airflow and ventilation in the living space by
opening windows as much as possible.
Health care settings
WHO provides guidance for the use of PPE, including masks,
by health care workers in the guidance document: Rational
use of PPE in the context of COVID-19.
24
Here we provide
advice for people visiting a health care setting:
Symptomatic people visiting a health care setting should:
•
Wear a medical mask while waiting in triage or other
areas and during transportation within the facility;
•
Not wear a medical mask when isolated in a single room,
but cover their mouth and nose when coughing or
sneezing with disposable paper tissues. Tissues must be
disposed of appropriately, and hand hygiene should be
performed immediately afterwards.
Health care workers should:
•
Wear a medical mask when entering a room where
patients with suspected or confirmed COVID-19 are
admitted.
•
Use a particulate respirator at least as protective as a US
National Institute for Occupational Safety and Health-
certified N95, European Union standard FFP2, or
equivalent, when performing or working in settings
where aerosol-generating procedures, such as tracheal
intubation, non-invasive ventilation, tracheotomy,
cardiopulmonary resuscitation, manual ventilation
before intubation, and bronchoscopy are performed.
•
Full infection prevention and control guidance for
health care workers is provided
One study that evaluated the use of cloth masks in a health
care facility found that health care workers using cotton cloth
masks were at increased risk of infection compared with those
who wore medical masks.
25
Therefore, cotton cloth masks are
not considered appropriate for health care workers. As for
other PPE items, if production of cloth masks for use in health
care settings is proposed locally in situations of shortage or
stock out, a local authority should assess the proposed PPE
according to specific minimum standards and technical
specifications.
Mask management
For any type of mask, appropriate use and disposal are
essential to ensure that they are effective and to avoid any
increase in transmission.
The following information on the correct use of masks is
derived from practices in health care settings
.
•
Place the mask carefully, ensuring it covers the mouth
and nose,
and tie it securely to minimize any gaps
between the face and the mask.
•
Avoid touching the mask while wearing it.
•
Remove the mask using the appropriate technique: do not
touch the front of the mask but untie it from behind.
•
After removal or whenever a used mask is inadvertently
touched, clean hands using an alcohol-based hand rub or
soap and water if hands are visibly dirty.
•
Replace masks as soon as they become damp with a new
clean, dry mask.
•
Do not re-use single-use masks.
•
Discard single-use masks after each use and dispose of
them immediately upon removal.
Advice on the use of masks in the context of COVID-19: interim guidance
-
4-
WHO continues to monitor the situation closely for any
changes that may affect this interim guidance. Should any
factors change, WHO will issue a further update. Otherwise,
this interim guidance document will expire 2 years after the
date of publication.
References
1. Water, sanitation, hygiene and waste management
for COVID-19
https://www.who.int/publications-
detail/water-sanitation-hygiene-and-waste-
2. Coronavirus disease 2019 (COVID-19) Situation
https://www.who.int/docs/default-
source/coronaviruse/situation-reports/20200402-
sitrep-73-covid-19.pdf?sfvrsn=5ae25bc7_6
3. Yu P, Zhu J, Zhang Z, Han Y. A familial cluster of
infection associated with the 2019 novel
coronavirus indicating possible person-to-person
transmission during the incubation period. J Infect
2020 doi:10.1093/jiaa077
4. Huang R, Xia J, Chen Y, Shan C, Wu C. A family
cluster of SARS-CoV-2 infection involving 11
patients in Nanjing, China Lancet Infect Dis 2020
doi: 10.1016/ S1473-3099(20)30147-X
5. Pan X, Chen D, Xia Y et al. Asymptomatic cases in
a family cluster with SARS-CoV-2 infection.
Lancet Infect Dis 2020 doi: 10.1016/ S1473-
3099(20)30114-6.
6. Tong Z-D, Tang A, Li K-F, Li P, Wang H-L, Yi J-
P, et al. Potential presymptomatic transmission of
SARS-CoV-2, Zhejiang Province, China, 2020.
Emerg Infect Dis. 2020 doi:
10.3201/eid2605.200198
7. Wei WE, Li Z, Chiew CJ, Yong SE, et al.
Presymptomatic Transmission of SARS-CoV-2 —
Singapore, January 23–March 16, 2020. MMWR, 1
April 2020/69.
8. Kimball A, Hatfield KM, Arons M, James A, et al.
Asymptomatic and Presymptomatic SARS-CoV-2
Infections in Residents of a Long-Term Care
Skilled Nursing Facility — King County,
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WHO/2019-nCoV/IPC_Masks/2020.3
