Quite a one-two-punch from 2 #COVID19 papers released today. First, a @ScienceMagazine paper estimates that most COVID19 infections are undocumented and unidentified through regular surveillance because they experience no, or only mild, symptoms.
Despite being less infectious than symptomatic/identified cases, undocumented cases contribute more to overall transmission than symptomatic cases due to their hidden nature. science.sciencemag.org/content/early/…
“the key findings, that 86% of infections went undocumented and that, per person, these undocumented infections were 55% as contagious as documented infections, could shift in other countries with different control, surveillance and reporting practices.”
The authors argue for countries to institute a “radical increase in the identification and isolation of currently undocumented infections” because that is the only way to fully control SARS-CoV2. That is what China and South Korea have done, for example.
It also underscores Tedros’ emphasis on testing at the WHO press conference earlier: “test, test, test” was the mantra. He may as well have been speaking directly to the US when he was saying that cnbc.com/2020/03/16/who…
A second paper, released by modelers at Imperial College, gazes into the future to estimate spread, mortality and hospitalization from #COVID19 in the UK and the US under different response scenarios. imperial.ac.uk/media/imperial…
The authors compare 2 response types: 1) mitigation: slowing the spread through social distancing and other measures without halting spread, and 2) suppression: meant to reverse the spread of the epidemic w/home isolation of cases & quarantines, along with social distancing.
The authors paint a dire picture of the future burden of cases and hospitalizations non-control or mitigation-only approach, even with good social distancing. The suppression approach still results in large # of cases & hospitalizations, but fewer than the other approaches.
This is graphic showing the modeled epidemic in the US under the various scenarios. Under the mitigation and suppression scenario, the peak is pushed out to the fall, instead of being in Spring/Summer. 
With mitigation the peak comes later (late 20/early 21) but is higher & resulting demand on hospitals higher. Under suppression, peak comes in the fall (Oct-Nov), and still exceeds health care capacity, but not as much under other scenarios.
Now, this is only a model. I would not expect things to play out exactly as illustrated here. But, it is very worthwhile to consider the implications for policy.
What both groups of authors point to is that the China/South Korea model of intense testing and case-finding, home isolation and quarantine, along with social distancing, is likely the most promising combination of interventions available for countries to address COVID19.
