Two years into the pandemic, most of us are fed up. COVID case charges are greater than they’ve ever been and hospitalisation charges are as soon as once more rising quickly in lots of international locations.
Towards this bleak image, we yearn to get again to regular. We’d like to fulfill pals in a pub or have them over for dinner. We’d like our struggling enterprise to thrive prefer it did earlier than the pandemic. We’d like our kids to return to their once-familiar routine of in-person education and after-school actions. We’d wish to journey on a bus, sing in a choir, get again to the gymnasium, or dance in a nightclub with out worry of catching COVID.
Which of those actions is protected? And the way protected precisely? These have been the questions we sought to reply in our newest analysis.
SARS-CoV-2, the virus that causes COVID, spreads primarily by airborne transmission. So the important thing to stopping transmission is to know how airborne particles behave, which requires information from physics and chemistry.
Air is a fluid made up of invisible, quickly and randomly shifting molecules, so airborne particles disperse over time indoors, similar to in a room or on a bus. An contaminated individual could exhale particles containing the virus, and the nearer you’re to them, the extra seemingly you’re to inhale some virus-containing particles. However the longer the interval you each spend within the room, the extra unfold out the virus will develop into. In case you are open air, the area is nearly infinite, so the virus doesn’t construct up in the identical manner. Nonetheless, somebody can nonetheless transmit the virus should you’re near them.
Viral particles will be emitted each time an contaminated individual breathes, however particularly if their respiration is deep (similar to when exercising) or entails vocalisation (similar to talking or singing). Whereas sporting a well-fitting masks reduces transmission as a result of the masks blocks the discharge of virus, the unmasked contaminated one who sits quietly in a nook is far much less more likely to infect you than one who approaches you and begins a heated argument.
All variants of SARS-CoV-2 are equally airborne, however the likelihood of catching COVID relies on the transmissibility (or contagiousness) of the variant (delta was extra contagious than earlier variants, however omicron is extra contagious nonetheless) and on how many individuals are at the moment contaminated (the prevalence of the illness). On the time of writing, greater than 97% of COVID infections within the UK are omicron and one individual in 15 is at the moment contaminated (prevalence 6.7%). Whereas omicron seems extra transmissible, it additionally appears to provide much less extreme sickness, particularly in vaccinated folks.
Probability of turning into contaminated
In our research, we now have quantified how the totally different influences on transmission change your danger of getting sick: viral components (transmissibility/prevalence), folks components (masked/unmasked, exercising/sitting, vocalising/quiet) and air-quality components (indoors/open air, massive room/small room, crowded/uncrowded, ventilated/unventilated). We did this by rigorously finding out empirical knowledge on how many individuals grew to become contaminated in superspreader occasions the place key parameters, such because the room measurement, room occupancy and air flow ranges, have been well-documented and by representing how transmission occurs with a mathematical mannequin.
The brand new chart, tailored from our paper and proven under, provides a share probability of turning into contaminated in numerous conditions.
A surefire method to catch COVID is to do a mix of issues that get you into the darkish purple cells within the desk. For instance:
Collect along with a lot of folks in an enclosed area with poor air high quality, similar to an under-ventilated gymnasium, nightclub or faculty classroom
Do one thing strenuous or rowdy similar to exercising, singing or shouting
Go away off your masks
Keep there for a very long time.
To keep away from catching COVID, strive holding within the inexperienced or amber areas within the desk. For instance:
If you happen to should meet different folks, accomplish that open air or in an area that’s well-ventilated or meet in an area the place the air flow is nice and air high quality is understood
Hold the variety of folks to a minimal
Spend the minimal potential period of time collectively
Don’t shout, sing or do heavy train
Put on high-quality, well-fitting masks from the time you enter the constructing to the time you allow.
Whereas the chart provides an estimated determine for every scenario, the precise danger will rely on the precise parameters, similar to precisely how many individuals are in a room of what measurement. If you happen to fancy placing in your individual knowledge for a specific setting and exercise, you may strive our COVID-19 Aerosol Transmission Estimator.