https://slatestarcodex.com/2020/03/19/coronalinks-3-19-20/
As before, feel free to treat this as an open thread for all coronavirus-related issues. Everything here is speculative and not intended as medical advice.
How many real cases?
As of today, the US has almost 10,000 official cases. How many real cases per official case?
One epidemiologist says 8x. In this US News article, scientists estimate 9000 true cases back when the official count was 600, suggesting 15x, and BBC estimates 10,000 real cases in the UK to 500 official ones, suggesting 20x. A study in Science (article, paper) estimates 86% are undetected, for about 7x. So it seems like most people are converging around 5 – 20.
Probably this number is different in every country, depending on their test rates. You're probably all already following the map of cases per country, but you can supplement with this map of how many tests each country is running per million people (h/t curryeater259 from the subreddit)
What about the evidence from famous people? If only 100,000 Americans are infected, it's pretty weird that it would hit both Tom Hanks and Idris Elba (also, Tormund from Game of Thrones). The Atlantic makes this case more formally. Given that Iran's vice-president is affected, what are the chances that only 1/12,000 of Iranians had the virus? Some people calculated it out and found that hundreds of thousands of Iranians must be affected for the prevalence among politicians to make sense, suggesting ratios of 100x or even 1000x.