Overall numbers won’t show the English strain coming

Here is a plot of daily new positive COVID tests in the U.S. in the first half of March 2020. It's no surprise that by mid-March, most people were worried: the virus was here and was growing fast. This was evident by the time there were 1,000 new positive tests per day. The lockdown began …

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Pooled COVID testing in the real world

[Thank you to Cathy Xue for proofreading and discussion.] In April I wrote about pooled testing. The basic idea is that instead of testing every swab individually, labs can pool samples together in groups of 10 (say) and test each mixture (pool) for the virus. For any pool that tests positive, they can then follow …

How to test and trace if you don’t have enough tests

[Edit: I now have a follow-up post that adapts this analysis to real-world constraints!] As we continue our worldwide fight with the coronavirus, many countries are looking to gradually transition away from strict lockdowns and toward effective test-and-trace programs. The idea is that if we can test people on a mass scale and track down …