Coronavirus: Hold the line

Georgia Ladbury
6 min readMar 28, 2020

As I stepped out onto the street for my daily walk this evening, I could hear nothing but birdsong. I live on a busy street in London, and at 6pm the road would normally be full of cars, engines whirring, horns beeping, indicators flashing. But today there was only emptiness, stillness, and birdsong. The message has got through, the world is on pause, and we are finally staying at home in anticipation of what’s to come.

And we need to hold the line.

If a week’s a long time in politics, it’s an even longer time in a pandemic. I was trying to remember how long it had been since the government ordered us all to stay at home, and did an internal double-take when I realised it was only four nights ago. It somehow seems like an age, partly because the pandemic has sped up, and partly because we as humans have slowed down — which is exactly what needed to happen if we are to get on top of this thing.

What we’re all doing right now is attempting to reduce the R0 of the virus. R0 is the term that epidemiologists use to describe the average number of people who will catch an infection from one contagious person. When R0 is above 1, an outbreak grows. When it’s below 1, it will eventually peter out. Coronavirus has an R0 of around 3 — i.e. on average, one infected person will infect three other people. It doesn’t sound very many, but think wider: those three people will each infect three other people, and those nine people will each infect three other people. By the time you’ve gone through ten iterations, that one first person has been responsible for infecting 59,000 people. That’s pretty staggering.

But coronavirus will only be able to do that if those 59,000 people are out there in the world and mixing with each other. If we all cease our social contacts, the virus has nowhere to go. R0 comes right down, and the outbreak begins to subside. This is why we have been ordered indoors, and only to socialise with our household members — because If you only see the same small group of people day in, day out, those wider contacts can’t happen and the virus can’t transmit further. Put simply: when we stop moving, the virus stops moving.

It takes a while, though. The incubation period for this coronavirus is estimated to be about 5–6 days, but can be up to 14 days. The day we started lockdown there will have been a number of people who were infected and unaware, and those people will go on to infect their household contacts. That means, for all the will in the…

Georgia Ladbury

I’m an infectious disease epidemiologist with special interest in zoonoses, new & emerging infectious, One Health, and interdisciplinary public health research