Tuesday/ numbers that grow exponentially

‘If you do the math, it gets very disturbing’, said Inslee. ‘In 7 to 8 weeks, there could be 64,000 people infected in the State of Washington if we don’t somehow slow down this epidemic. And the next week, it’s 120,000 — and the next week, it’d be a quarter of a million’.
– Washington State Governor Jay Inslee, Tue. Mar 10, 2020.

Washington State Governor Jay Inslee will announce tomorrow that all gatherings of more than 250 people, are banned in the Seattle metro area. The current coronavirus numbers may seem small: a total of 267 infections in Washington State (24 deaths).

The trouble is —
1. the real number might be a lot bigger, and
2. if left unchecked, infected persons can each infect between 2 and 3 others, making for exponential growth in the number of infections.

Check out the graph below: my own rough calculation starting with the 267, and repeatedly multiplying by 2.5 each week.  We know know that an infected person will typically start to show symptoms some 5-6 days after exposure.

For this graph I assumed a starting number of 267, and that the number grows by 2.5x every week. It shows that 267 becomes 670 after a week, then 1,700. It takes a shockingly short time to get to 10,000 from there, and then only 3 weeks to 100,000+.

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