Advertisement

Coronavirus: Why the UK had to enforce a lockdown - and what would have happened without it

Boris Johnson has effectively put the whole of the UK under lockdown to slow the spread of the coronavirus.

The prime minister said the stricter measures were vital to prevent too many people becoming ill from COVID-19 and overwhelming the NHS.

So why did the government decide to act now? Part of the reason can be found by comparing the UK outbreak to the ones in Italy and Spain.

The above chart shows the coronavirus deaths in each country from the day each one reported its first death.

It uses a logarithmic scale, so the distance between one and 10 is the same as between 10 and 100.

This allows us to see how fast the number of deaths is increasing, instead of just the total number.

Looking at the data like this shows that the growth rate of the disease in the UK and Italy is similar.

This is true even though the UK has fewer total deaths than Spain or Italy - as the chart below illustrates.

Given the similarities between the outbreaks in the UK and Italy, it is not surprising that the UK government decided to act at a similar time to the Italian government.

In Italy, the government imposed a lockdown on day 17, while in the UK it happened on day 18.

The number of deaths has continued to increase in Italy despite the lockdown, but the rate has begun to slow in some places.

:: Listen to the Daily podcast on Apple Podcasts, Google Podcasts, Spotify, Spreaker.

The UK government therefore had little choice but to also impose a lockdown if they wanted to keep the growth rate of the disease at a manageable level.

Otherwise the outbreak in the UK would almost certainly have become worse than that in Italy.

The first chart also explains why the Spanish government imposed a lockdown earlier than the other two countries, as the number of deaths rose more quickly there than elsewhere.

Another possible reason the UK government decided to act now is the fact that people weren't following the social distancing guidelines as rigorously as needed.

Tuesday has seen the biggest rise in UK coronavirus deaths, despite social distancing guidelines being introduced a week ago.

The government may have felt they therefore had little choice but to enforce stricter measures, which are critical to slow the spread of the disease.

The above chart shows how quickly the disease spreads if each person infected with the coronavirus infects between two and three other people, as is currently thought to happen.

But imposing a lockdown could help reduce that number to less than one, which would mean that, given time, the spread of the disease could be stopped.

The total eradication of the disease would take a very long time, but that does not mean measures cannot have immediate effects.

Even if they only slow the spread of the disease they can still improve our ability to provide medical help to those that need it.

Reducing the number of people who have the disease at any one time will reduce the amount of doctors, nurses and intensive care beds needed to care for those who get seriously ill.

This is crucial as once the NHS becomes overrun with patients, people who might otherwise have been able to survive run the risk of dying from the disease.

Lockdowns are therefore a vital way of making sure the spread of the disease is stopped and that people who do get the disease have the best possible chance of survival.

Methodology of the social distancing model:

This is an SEIR model developed by Jessica Bridgen, a PhD student at Lancaster University. The model shows an epidemic of an infectious disease with the current best estimated characteristics of COVID-19 in a single county of the UK, with a population size of approximately 1.1 million, and starting with 100 people infected. The model assumes a R0 of 2.2, an average latent period of five days (similar to the incubation period) and an average infectious period of five days.

Why not plot the y-axis? The model illustrates how social distancing as an intervention could affect the number of cases during an epidemic, but it is not a predictive tool. To avoid misunderstanding, we have decided not to show the total number of cases predicted by the model, but instead how social distancing can shift the dynamics of an epidemic.