If an infectious pathogen spreads predominantly through large
respiratory droplets that fall quickly, the most important public health
measures are:
respiratory hygiene (e.g. sneezing into tissues)
disinfecting surfaces and objects (fomites) onto which droplets may
have fallen
reducing direct contact (e.g. do not shake hands with others or touch
one’s own face)
staying physically apart from others at a distance that reflects the
effect of gravity on droplets (1-2 metres)
wearing facemasks within that droplet distance
physical barriers (such as visors of plastic screens)
providing respirator-grade protection for healthcare staff who
undertake so-called “aerosol-generating” procedures. These contact, droplet and fomite precautions do not distinguish between
indoor and outdoor settings, since a gravity-driven mechanism for
transmission would operate similarly in both.
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If an infectious pathogen is mainly airborne, a person could potentially
be infected when they inhale aerosols emitted in the breath of an
infected person. These aerosols may remain suspended in the air for many
hours. Reducing airborne transmission requires measures to avoid
inhalation of infectious aerosols, including
engineering controls in indoor spaces (ventilation, air filtration)
reducing crowding (e.g. by encouraging people to work from home if
possible)
reducing time spent indoors (e.g. frequent breaks for school classes)
maximising physical distance between people indoors (even beyond 2
metres)
wearing masks whenever indoors
careful attention to mask quality (to maximise filtration) and fit (to
avoid air getting in via gaps)
taking particular care in indoor activities that generate aerosols
(e.g. speaking, singing, exercising)
providing respirator-grade protection for health-care staff and other
front-line workers
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