Until the mid-1800s, doctors didn’t bother washing their hands – they would go from dissecting a cadaver to delivering a child. Then a Hungarian medic made an essential, much-resisted breakthrough

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It felt strange when Boris Johnson emerged from the first Covid-19 Cobra meeting on 2 March and told us to wash our hands while singing Happy Birthday. The preppers among us had panic-shopped while awaiting his pronouncements, and others fretted about vulnerable loved ones, travel plans, the nightmare of simultaneous homeworking and home-schooling, and not being able to work at all. And all our leader had was this?

As one of the few things we can do to significantly stop the spread of coronavirus while out in the infectious world, the new rules for this everyday habit have become the meme du jour. The Killers’ frontman, Brandon Flowers, tweeted a video of himself lathering up while crooning his hit Mr Brightside to 4 million followers. Judi Dench and Gyles Brandreth have posted themselves online reciting The Owl and the Pussycat with sudsy hands. A website for generating handwashing infographics to the song lyrics of your choice has gone viral.

The WHO has declared the Covid-19 outbreak to be a pandemic. But what does that mean?

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Declaring a pandemic has nothing to do with changes to the characteristics of a disease, but is instead associated with concerns over its geographic spread. According to the World Health Organization, a pandemic is declared when a new disease for which people do not have immunity spreads around the world beyond expectations.

The WHO has declared the Covid-19 outbreak to be a pandemic. But what does that mean?

• Coronavirus latest - live updates

Declaring a pandemic has nothing to do with changes to the characteristics of a disease, but is instead associated with concerns over its geographic spread. According to the World Health Organization, a pandemic is declared when a new disease for which people do not have immunity spreads around the world beyond expectations.

Yes, Covid-19 is serious, but context is key and the world is well placed to deal with it

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The coronavirus epidemic plainly poses an exceptionally serious global problem: in a few short weeks, it has spread from China to more than 80 countries, infecting more than 100,000 people so far and causing more than 3,400 deaths.

But as we are hit with minute-by-minute updates from around the world, experiencing the advance of Covid-19 in real time – news alerts, huge headlines, social media hysteria – there’s a risk that we might lose some essential context.

The truth about the protective value of face masks and whether it’s easy to catch Covid-19

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All viruses accumulate mutations over time and the virus that causes Covid-19 is no different. How widespread different strains of a virus become depends on natural selection – the versions that can propagate quickest and replicate effectively in the body will be the most “successful”. This doesn’t necessarily mean most dangerous for people though, as viruses that kill people rapidly or make them so sick that they are incapacitated may be less likely to be transmitted.