How we re-open New York City now (or very soon).

May 15, 2020 By Alan Salzberg

We are squandering time and killing the economy.  But that’s unnecessary.  We can get back to work safely almost immediately.  Here’s how.

The main piece of the puzzle is a COVID tracker app, which would be required for subway entry, as well as entry into all commercial establishments and public buildings.  Small businesses can self-enforce, but larger business and office buildings (we can decide how large is large) are required to check the app at the door.  We don’t need to build this app.  This app, in many forms, has already rolled out in many countries around the world, and can vary in terms of its intrusiveness.  See the MIT technology review for a tracker app tracker: .

Who gets a free pass from the app?

  • Positive Antibody Test or positive COVID test (and recovered at least 20 days prior).

New York got hit hard with the virus, likely in part as a result of acting too late, as many articles have pointed out ( ).   But now we have a big advantage: more than 2 million people got the virus and now have antibodies (see this study that says almost everyone who gets the virus develops antibodies: ).  These people can safely go back to work -- no masks, no social distancing.  They cannot get infected or transmit the virus, at least for a short time and possible for a long time. 

Antibody tests are imperfect, but the best of them have false positive rates of 5%.  This means that, in a population like NYC with 25% infected, of those who test positive in random tests, about 87% will have antibodies (and while we restrict these tests to those who have had symptoms, it will be higher than 87%).  This is an acceptable rate because it will still ensure herd immunity, even if around 13% are walking around without antibodies (for more about this calculation see my former post: ).   It will likely be a long time before everyone who was infected can get an antibody test, but as a growing number get them, it allows more people to get back to work.

If you had COVID and recovered completely, you will get antibodies, so we should extend the free pass to those who have had it, as long as they have had time to recover and get antibodies. Here’s a chart of the antibody tests, showing that almost everyone has significant antibodies 20 days post onset: ).

  • Thermal Thermometer Check.

You should really never go to work sick, but a thermal thermometer check keeps us honest.  There are 472 subway stations, so we could have the check at every station.  We could deploy 5 thermometers on average per station.  Each could test around 3 people a minute.  This would require about 2,500 thermometers and 10,000 workers (if the subway is open close to 24 hours, then we need at least 4 people full time to fill a 168 hour week).  This allows for about 300,000 tests an hour if we can do 2 per thermometer per minute.  There could also be other places with official check points throughout the city.

Once you’ve had a safe temperature reading, you have 12 hours before you need a new one.  As infection rates decline, this could be increased to 24 hours or more.  In order to get a reading, the individual needs to produce a code from their COVID tracking app, and then the result comes with an accompanying code.  This prevents cheating: without this people could get tested multiple times and take advantage of false positives.

Temperature checks are not perfect because people get COVID without a fever and are infectious for a short period of time before they get a fever, but they are used and working as a part of a strategy to prevent infection.  See this article for more about the pitfalls: .

Ideally, the temperature check will be replaced by a COVID test that could be performed at home, with quick results, but we are not there yet.  A negative COVID test could allow contact for a couple of days instead of 12 hours, because it takes time after infection to become contagious (and therefore someone not infected in the morning would not be contagious in the evening even if, say, they got infected during the day).

What else does the app do? 

The app tracks who you were in close physical contact with.  Anyone who has had contact with someone with a positive COVID test will get an immediate notification.  They would need to then leave work as soon as possible (with some reasonable time window), and then stay home for a certain period of time, depending on when the contact occurred, after which they would need to be tested for COVID.  A negative test is a get out of jail free card.  We are currently doing 30,000 tests a day, so this procedure is currently doable.

So that’s the plan.  Though I changed some parts of it, I didn’t make this plan up.  It is taken from European and Asian plans, some of which have already proven effective.