How does COVID-19 spread? The Top 5 things everyone should know by now.
You’d be very hard-pressed to find anyone on the planet who hasn’t heard of COVID-19, with every country in the world recording at least one case, and most having national outbreaks in multiple waves. You would think therefore that most of us would be fairly clued-up about COVID-19 by now.
However, our knowledge and information about SARS-CoV-2 has progressed considerably, while in step so has misinformation — leading many of us to be mired in a quagmire of fake news about the virus.
As many countries start to unlock their national measures once again, we could all take a little refresher course to brush up on the basics. So here is the Top 5 Things everyone should know about the spread of COVID-19*.
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- COVID is in the AIR
As a respiratory virus the commonest way COVID-19 spreads from person to person is via respiratory ‘droplets’, big clumps of virus that are made when someone coughs, sneezes, talks, shouts, cries, blows their nose, eats or hiccoughs. The smallest droplets, called ‘aerosols’ can last in the air for several hours after being produced, ready for the next person to breathe them in and become infected.
While there is still some debate about this, the most cautious approach is to think of COVID-19 like smoke, it’s in the air and you should do your best to avoid inhaling it.
2. In order to be infected, you need to inhale more than just one particle
There is a threshold of the ‘dose’ of virus that you inhale that will lead you to becoming infected. The principle is the MORE you are exposed, the MORE likely you will be infected. Therefore a LARGE dose or multiple SMALL DOSES over a short period of time will lead to the same result; infection.
Therefore TIME EXPOSED is as important as the AMOUNT you are exposed to. i.e. if you spend HOURS in a crowded BAR you are far more likely to be infected by COVID than if you spend MINUTES in a socially distanced SHOP.
3. Ventilation is salvation
Just like when you burn your toast, and you open a window to clear the smoke, opening a window helps clear COVID aerosols. We can measure how good ventilation is by thinking about how many times an hour all the old air in a room is exchanged for fresh air. In newer hospitals this is tightly controlled, with air exchangers that cycle the air 4–5 times an hour or more. Opening a window vastly increases this exchange of air, removing the COVID and bringing in clean fresh air. Obviously, the best place for ventilation is outside, where COVID particles are nearly immediately diluted and dissipated, just like smoke. The virus itself loses the ability to infect others fairly quickly in the outside world, in a matter of hours.
So we can add ventilation to our calculation and look at situations like this:
Risk of infection = time EXPOSED + number and proximity of other people + degree of ventilation
4. Behaviour is your saviour
What modifies this calculation is our behaviours — from wearing masks, which limits aerosol production for others, to socially distancing, which reduces the number of people within the range of any aerosols produced. Talking loudly and eating adds to aerosol production, while drinking makes socially distancing more difficult — both problems found in hospitality. Similarly, al fresco drinking or dining is much safer, as outside is a very well ventilated space.
We can all make the spread of COVID much less likely by modifying our behaviours — sticking to these rules means we can do more of our normal lives without risking resurgence of the pandemic.
5. Wash your hands
COVID can also be spread on surfaces, although the likelihood of this appears to be less than was thought initially. Washing your hands effectively kills the virus simply and easily, with alcohol gel or soap, and can stop you spreading the virus onto others by touching them. COVID is also in your poop, and scientists have been monitoring the severity of a local outbreak by measuring the levels of COVID-19 in the sewer system. Which isn’t particularly useful, just interesting, and a reminder once again, to WASH YOUR HANDS.
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By remembering these 5 things we can all make our lives easier and safer as countries open up back to normal life. Keep your distance, wash your hands, open a window or meet outside, wear a mask, and reduce your time in potentially infectious situations.
Lastly, whatever the mode of spread of COVID-19, the best way to reduce the risk of infection is to reduce the levels of COVID-19 overall. If just one person in 1000 is infected, your chance of actually coming in to contact with COVID is very slim. In that scenario even if you took no precautions at all, you are unlikely to ever meet the person with COVID anyway, so your risk is low.
Similarly imagine one person in 10 is infected, your chance of meeting someone with COVID is much higher. In that scenario, your precautions are much more important, as you are likely to come face to face with COVID perhaps daily if not more, so you have to be far more careful.
Countries with No COVID are back to normal life now — open bars, tens of thousands attending concerts, freely socialising, hospitality fully open. That could be your country as well, if we all understood and acted on these 5 things, together.
[*COVID-19 is the disease, while SARS-CoV-2 is the VIRUS, but for simplicity and translation I’ve used the term COVID to refer to both here.)
Dr Dominic Pimenta is a UK-based physician, author and researcher. His book about working in COVID ICU during the first wave in the UK is out now “Duty of Care”, with all sales royalties going to the charity he co-founded, the Healthcare Workers’ Foundation, supporting the welfare and wellbeing of healthcare workers in the UK through the pandemic and long into the future.
