COVID-19, Christmas and Risk Analysis

Please note that this article was written BEFORE any vaccine was made available.

As a Laser Protection Adviser I carry our Risk Analyses routinely, so I’m not too bad at doing them.

So I thought I’d discuss how to analyse a situation in the current pandemic.

Risk Analysis is a set of tasks that must be carried out to try to evaluate the possible risk that an individual (or individuals) may be exposed to in certain situations.

How do we calculate ‘Risk’:


Risk is composed of two parts – likelihood and severity.

Likelihood is simply the probability that an event might occur. You are most unlikely to be hit by a bus if you’re not near a road!

But, likelihood can be difficult to calculate accurately. Many people overestimate or underestimate likelihood, because they have little to no experience in doing this.

Many also come up with wildly wrong numbers because of a lack of understanding or knowledge. Or, sometimes it is due to misinformation – which is all the rage on social media these days!!


Severity is a measure of how badly affected someone may be if the likelihood is 100%. Or, in the case of a virus like COVID-19, they contract it.

There is a lot of research currently underway across the world into the effects of COVID-19, but the severity of infection appears to be linked to the ‘infectious dose’ – this is the amount of virus which a newly infected person may contract.

LowLittle to no symptoms. No lasting effects.
MediumMedium to bad symptoms. Ill for a medium to long period. Possible hospitalisation. Unable to work or live normally for a signifiant period of time.
HighDeath or ‘long Covid’. A lifetime of illness or fatigue.
Severity increases with age and co-morbidity.

So, let’s look at a particular situation and do a quick analysis.

Imagine a family meal setting – in a house – with some extended family members. Let’s say it’s a Christmas dinner setting and assume that at least one person is shedding virus.

How do the numbers stack up?

PointLikelihood any individual of contracting the virus
Number of infected peopleIncreases with this number
Size of roomIncreases as room is smaller
Closed windowsIncreases – poor ventilation
Time spentIncreases linearly with time – the more time together, the higher the risk
Singing, laughing, shoutingIncreases the amount of virus in the air
Hugs and kissesIncreases
Natural immunityThere is ZERO natural immunity to COVID-19! (according to current research)

This is quite depressing! But it’s the same for all respiratory viruses. We’ve known this for a very long time…

Of course, if nobody in the room has the virus, then the likelihood of cross-infection is zero. But, if only one person has it, then it is highly likely that others will become infected. That number depends on the ‘infectious dose’ and at what stage the infected person is.

Research clearly shows that around 70% of all COVID-19 infections occur during the ‘pre-symptom’ phase when the carrier is unaware they have it. Somewhere between 80 to 95% of infections are likely due to breathing in infected air!

Asymptomatic people can shed this virus without ever knowing they had it – they will not develop any symptoms, but can infect many others!!


The reality is that life is a risk. Every day we do ‘risky’ things, even if it’s just going for a walk. But we all do risk analyses all the time. Its a survival trait!

So, if you’re planning to have the family round for Christmas this year, at a time when the pandemic has such a grip on the country, then please do the above evaluations.

Try to mitigate against the likelihood of contraction by:

limiting the numbers,

limiting the time,

eating outside if possible,

if you can’t then open all your windows,

wear masks when not eating,

using a large room with lots of ventilation,

if exhibiting ANY signs of infection (COVID-19 or other), DO NOT ATTEND!!!


This virus is ‘unfair’. It is upsetting a lot of people. But the virus doesn’t ‘care’.

Finally, three important points to consider:

  1. the virus is not trying to ‘kill’ anyone! That’s not how viruses work.
  2. most deaths occur because the host’s body is already compromised with other problems (co-morbidities). They simply cannot fight the virus while in such a condition and their body gives up!
  3. if an infected person is taken into ICU, they only have around a 50% chance of emerging alive. If they do survive, they will then suffer longterm consequences of this disease.

We often hear the phrase ‘stay safe’ these days.

Hopefully, the above will help you to do just that.


Physicist and bioengineer.

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