Thread on something really important.
At the outset of the pandemic, @DrMikeRyan called on us to "break the chains of transmission".
We haven't. The chains now number over 100,000,000 people.
Why? A central measure is often overlooked: isolating those exposed to the virus.

The above graph by @Paul5cott compares policy measures around the world on isolation and quarantine.
A lot of focus has been on reducing the random seeding of new chains of transmission through travel.
That's important - but only one part of containing Covid-19 spread.

It sounds simple: if everyone who currently has the virus right now could be kept separate from other people for about two weeks, infections would drop to zero. Pandemic over.
But individuals cannot achieve it alone. Isolation only works within a system of support and enforcement

Survey data shows that a very low percentage of people who are just 'told' to self-isolate actually do it.
A study of 32,000 people in the UK over three months last year found only 18% of them actually kept away from others. In the Netherlands, data indicates it's about 44%.

A large proportion of those who ventured out despite being warned they had been exposed to Covid-19 did so to go to work.
Others have to buy groceries, or medicines, or need something for their child.
It's not just people being dicks -- they need support.