Thread by @davidrliu

Bizarrely, @CDCgov now says Americans don’t need to get tested even if they have been in close contact with a #COVID19 infection, and that asymptomatic people do not need a test. More Americans will needlessly die as a result. Here's a thread on why testing is essential. (1/12)

From one of the most accurate #COVID19 models to date (@youyanggu's covid19-projections.com/#current-us-pr…), about 1 in 75 Americans today has an active #COVID19 infection. Many of these are asymptomatic and unaware they are infected, but can still infect others. (2/12) nejm.org/doi/full/10.10…

Without identifying the 1/75 who has an active infection and separating them from the 74/75 who do not, we either allow the 1/75 to mix with others, causing new outbreaks and adding to 180,000 US deaths, or we lockdown, even though 74/75 lack the virus. Neither is acceptable.3/12

If instead we can identify the infected 1/75 Americans and isolate them for just 10-14 days, the pandemic would be extinguished, because the #SARSCoV2 virus that causes #COVID19 must find a new human host every ~10 days, or it will cease to propagate. This is its weakness. (4/12)

Example: if one infected person infects 2 others every 6 d, the # of infected people multiples ~100x in 36 d (top). But if we identify 4 of 9 infectious people and isolate them so they each infect only 1 other instead of 2, the # of infectious people at day 36 is ~9 (bottom).5/12

How do we identify the 1/75 infected Americans so we can isolate them and break the chain of transmission? Through VIRUS TESTING. There are multiple ways to test for the #SARSCoV2 virus, including RT-PCR testing, RT-LAMP testing, antigen testing, and many variations. (6/12)

Each offers strengths and weaknesses. Every week new tests offer better performance, lower cost, and fewer requirements, making their large-scale use easier. For example, yesterday, @AbbottNews announced FDA EUA approval of a 15-minute antigen test. (7/12) cnn.com/2020/08/27/inv…

Thanks to the hard work of many scientists and partners, several testing platforms—with proper federal support—could be widely deployed to identify infected Americans and snuff out the pandemic. Others have used this strategy to defeat the pandemic, including the NBA bubble.8/12

In fact, some of our leaders test themselves and those around them multiple times a week to minimize their risk of getting infected. The same strategy could protect all Americans, if we had access to effective testing with rapid turnaround time. (9/12) cnbc.com/2020/08/03/whi…

A nationally coordinated testing strategy is especially important to minimize supply chain problems, and because #COVID19 transmissions within the US come from places near and far. This map shows transmissions in the US from genomic epidemiology. (10/12)
nextstrain.org/ncov/north-ame……

Since mitigation alone has not been sufficient in the US, if we do not identify and isolate the infected, we are left with vaccines. While early data is promising, we don’t yet know if vaccines will be safe and effective, and they won’t be available to most until 2021. (11/12)

The best weapons we have to fight the pandemic now are to reduce the opportunity to spread the virus by wearing masks, distancing, and identifying infected people through TESTING as many Americans as possible so we can break transmission chains and restore our way of life. 12/12