• Pravin Chalak

Your New Weapon - Mask


Advice on the use of masks in the context of COVID-19

Interim guidance

5 June 2020

This document is an update of the guidance published on 6

April 2020 and includes updated scientific evidence relevant

to the use of masks for preventing transmission of

Coronavirus disease 2019 (COVID-19) as well as practical

considerations. The main differences from the previous

version include the following:

• Updated information on transmission from

symptomatic, pre-symptomatic and asymptomatic

people infected with COVID-19, as well as an

update of the evidence of all sections of this


• New guidance on the targeted continuous use of

medical masks by health workers working in clinical

areas in health facilities in geographical areas with

community transmission1 of COVID-19;

• Updated guidance and practical advice for decision-

makers on the use of medical and non-medical

masks by the general public using a risk-based


• New guidance on non-medical mask features and

characteristics, including choice of fabric, number

and combination of layers, shape, coating and


Guidance and recommendations included in this document

are based on previous WHO guidelines (in particular the

WHO Guidelines on infection prevention and control of

epidemic- and pandemic-prone acute respiratory infections in

health care) (1) and the evaluation of current evidence by the

WHO ad hoc COVID-19 IPC Guidance Development Group

(COVID-19 IPC GDG) that meets at least once a week. The

process of interim guidance development during emergencies

consists of a transparent and robust process of evaluation of

the available evidence on benefits and harms, synthetized

through expedited systematic reviews and expert consensus-

building facilitated by methodologists. This process also

considers, as much as possible, potential resource

implications, values and preferences, feasibility, equity,

ethics and research gaps.

Purpose of the guidance

This document provides guidance to decision makers, public

health and IPC professionals, health care managers, and

health workers on the use of medical and non-medical masks

in health care (including long-term care and residential)

1 Defined by WHO as “experiencing larger outbreaks of local

transmission defined through an assessment of factors including,

but not limited to: large numbers of cases not linkable to

transmission chains; large numbers of cases from sentinel

settings, for the general public, and during home care. It will

be revised as more data become available.


The use of masks is part of a comprehensive package of the

prevention and control measures that can limit the spread of

certain respiratory viral diseases, including COVID-19.

Masks can be used either for protection of healthy persons

(worn to protect oneself when in contact with an infected

individual) or for source control (worn by an infected

individual to prevent onward transmission).

However, the use of a mask alone is insufficient to provide an

adequate level of protection or source control, and other

personal and community level measures should also be

adopted to suppress transmission of respiratory viruses.

Whether or not masks are used, compliance with hand

hygiene, physical distancing and other infection prevention

and control (IPC) measures are critical to prevent human-to-

human transmission of COVID-19.

This document provides information and guidance on the use

of masks in health care settings, for the general public, and

during home care. The World Health Organization (WHO)

has developed specific guidance on IPC strategies for health

care settings (2), long-term care facilities (LTCF) (3), and

home care.(4)

Transmission of COVID-19

Knowledge about transmission of the COVID-19 virus is

accumulating every day. COVID-19 is primarily a respiratory

disease and the spectrum of infection with this virus can range

from people with very mild, non-respiratory symptoms to

severe acute respiratory illness, sepsis with organ dysfunction

and death. Some people infected have reported no symptoms

at all.

According to the current evidence, COVID-19 virus is

primarily transmitted between people via respiratory droplets

and contact routes. Droplet transmission occurs when a

person is in close contact (within 1 metre) with an infected

person and exposure to potentially infective respiratory

droplets occurs, for example, through coughing, sneezing or

very close personal contact resulting in the inoculation of

entry portals such as the mouth, nose or conjunctivae

surveillance; and/or multiple unrelated clusters in several areas of

the country/territory/area” (https://www.who.int/publications-




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