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Why early lockdown mattered
- 1. WHY EARLY LOCKDOWN MATTERED @thisfionaweir #covid19 #coronavirus
- 3. AND WE’VE HEARD HOW DIFFERENT MEASURES MAY HELP… • Hand-washing • Staying at home if we feel unwell • Social distancing • Lockdown • Etc.
- 4. MANY EXPLANATIONS SUGGEST THAT CASE NUMBERS FLATTEN EVENLY, WHENEVER THE MEASURE IS INTRODUCED…
- 5. BUT THAT ISN’T SO. IT MATTERS WHEN MEASURES ARE INTRODUCED. IT REALLY MATTERS. Here? Or here? Or here?
- 7. FIRSTLY, IT IS TO DO WITH HOW MANY CASES THERE ARE AT THE TIME… (LOOK AT THE CROSSES) A few Many more
- 8. WHEN THERE ARE FEW CASES, LOCKDOWN CAN BE VERY EFFECTIVE. • If, say, lockdown causes a 20% reduction in cases… • And there are just 10 cases… • Then there are only 8 people left to spread the infection
- 9. WHEN THERE ARE LOTS OF CASES, LOCKDOWN HAS TO BE MUCH MORE COMPLETE TO HAVE THE SAME EFFECT. • But a 20% reduction in cases when there are 1000 cases… • Means there are still 800 people left spreading the infection. • To have only 8 people left out of 1000 would be almost impossible: you’d need the lockdown to achieve a 99.2% reduction.
- 10. SECONDLY, IT IS TO DO WITH HOW FAST THE INFECTION IS SPREADING… (YOU CAN TELL BY HOW STEEP THE CURVE IS) Slowly Faster
- 11. EXPONENTIAL GROWTH MEANS CASES INCREASE VERY, VERY FAST. • When every person passes the infection to 3 others within 5 days... • 8 people will infect 24 others • Then 24 people will infect 72 others • 72 people will infect 216 others • 216 people will infect 648 • 648 people will infect 1944 • And so on. You get from 8 infected people to thousands in just a few weeks.
- 12. EARLY ACTION IS VITAL TO STOP EXPONENTIAL- READ OF INFECTION . • When every person passes the infection to 3 others within 5 days... • If only 8 people are infected, you will have 1944 infected after 25 days. • If 800 people are infected, you may have 194,400 infected after 25 days.
- 13. THIS ANIMATION ALSO SHOWS WHY EARLY ACTION IS MORE EFFECTIVE THAN LATER ACTION
- 14. SO… • Covid-19 was spreading exponentially before lockdown • Lockdown slowed the growth • Earlier lockdown when there were fewer cases would have meant thousands fewer cases and deaths. thisfionaweir 2020