Decision-makers at the federal, state and provincial levels around the globe:

As scientists, researchers, health care professionals, and concerned citizens, we call upon you to fully lock down your jurisdictions now, without further delay, to reduce the spread of SARS-CoV-2 and the disease that it causes, COVID-19. Every hour we wait makes the problem exponentially worse, with estimates of millions of deaths. Only with drastic measures can we significantly reduce the number of new cases.

Every day, new research makes the following fact clearer: policies that only quarantine symptomatic people simply aren’t enough to slow the tide.

• Community transmission via undocumented cases is much more widespread than previously thought and is a major reason this pandemic is growing at an exponential rate. New evidence on community transmission was released in a March 16 article published by some of the world’s leading epidemiologists in the prestigious academic journal Science (available here). 
• Asymptomatic carriers, not likely to be identified, are now confirmed by leading researchers as a major source of spread. According to the epidemiologists’ analysis, asymptomatic (and hence undocumented) infections were responsible for 79% of documented cases in the recent COVID outbreak in China. The study estimates that for every known case of coronavirus, another 5 to 10 cases are likely to be undetected. See this coverage in the New York Times, aptly titled: “Coronavirus is hiding in plain sight.”
• Lockdown will save tens or possibly hundreds of thousands of lives, as shown in new public health simulation models by Imperial College London. See this article in The Guardian, which explains why this study has changed UK policy. See this article in the New York Times about how these findings have influenced US policy (including the recommendations from the White House task force).

As a matter of urgency, we recommend that a policy of maximal mitigation be implemented immediately, including the following actions, in keeping with the Imperial College London study:

1. All universities, colleges, schools, and daycares should be closed. 
2. Restrictions on domestic and international travel should be implemented immediately, including planes, trains, and public transit (except for emergency workers and essential services).
3. Regions with confirmed community transmission should follow San Francisco’s example and impose “shelter in place” requirements for all residents; including closure of all public facilities, non-essential businesses, and private and public gathering places. Urgent support should be provided for vulnerable individuals who may be inadequately housed or homeless. 

Clearly, these actions will have significant impacts on economic wellbeing, but we believe that the unprecedented nature of the COVID19 threat to our health and health care system requires equally unprecedented responses. 

At this point, as many nations have already come to accept, full lockdown is inevitable. Every day (and even every hour) of delay in implementing lockdown will cost lives. 

Spread these words, not the virus. Sign, then share.

Sincerely,

Karen Bakker, Ph.D., Professor and Canada Research Chair, University of British Columbia

Gary Marcus, Ph.D., CEO Robust.AI, Professor Emeritus, New York University

Dr. Michael Joyner, Mayo Clinic

Dr. Derya Unatmaz, Professor, The Jackson Laboratory

Dr. Saif S. Rathore, MD, Ph.D., MPH, Clinical epidemiologist

Dr. Carlos del Rio, Professor and Chair, Department of Public Health; Professor, Department of Medicine, Emory University

Nathaniel Daw, Ph.D., Professor, Princeton University

Dr. David Fisman, University of Toronto

Dr. Lili Barouch, Professor, Johns Hopkins

Dr. Samira Rahimi Ph.D., Professor, McGill University

Tom Dietterich, Professor, University of Oregon

Sean Hill, Professor, University of Toronto

Toby Walsh, Professor, UNSW Sydney

Michael Witbrock, Professor, University of Auckland

Alan Mackworth, Ph.D, Professor Emeritus, University of British Columbia

Philippe Le Billon, Ph.D. Professor, University of British Columbia