April 20 - COVID-19 in Westchester County, NY

Two critical pieces of data from Westchester's epidemic seem to contradict each other. The rate of new cases has not slowed down, but the hospitalization rate has slowed???  If the infection rate has not slowed down (as evidenced by new cases) then the number of hospitalizations should not be slowing down? (Westchester does not report hospitalization data, but both the state and NYC report decreases in hospitalization.)

New Cases per Day in the NYC Metro Area since start of epidemic

NYS Total Hospitalizations

Possible explanations for this discrepancy are that the test data for new cases is more delayed than the hospitalization data OR that fewer new cases require hospitalization. No one has explained this.

The Percent-Testing-Positive in the NYC metro area continues to drop, but it is nowhere near the national average of about 15%.

There is no change in the comparison of Bergamo, Italy with Westchester County.

The daily death count in Westchester (and in NYS) has not yet started to substantially drop.

How immune is Westchester?

Westchester has more infections per capita than any county in the US (including NYC).  Nassau county is not far behind.  [Why would these less dense places with healthier populations be harder-hit than NYC?] Almost 2.5% of the Westchester population is confirmed infected.  7.5% of Westchester has been tested for the virus.  [Compare that with 1% nationally.] 

The true measure of immunity will come after a random antibody testing study is started this week.  It is rumored to include 3000 households in NYC (which should be comparable to Westchester). In addition, Northwell Health Core Labs (Long Island) is committing to start antibody testing this week at 10,000 tests per day, increasing to over 100,000 per week.

Germany is doing a similar study of 3000 households in the most hard-hit areas.  No results yet.

One sneak peak at what this might look at comes from a study of about 200 birth mothers in NYC in the past month.  Four had symptoms of COVID and tested positive. (Note that is about the same as the 2.5% confirmed in Westchester.)  Testing of the other 200 mothers revealed another 29 positives who were asymptomic, or 15%.  Once again, this does not detect any persons that may have already recovered from the disease. It is very likely that 20% of Westchester have the antibody.  What if there is 50% of the population who is naturally immune for some reason? That would be getting close to herd immunity.

Reopening

As states start to think about reopening places where human contact is more likely, it would be useful to know which types of behaviors are the most effective at preventing transmission. Is it masks?  Is it gloves? Is it not touching your face? Is transmission by air more likely than transmission by touch? Are people using cash more likely to get infected? Shaking hands and opening doors can be avoided. But what about floors and shoes? Should I handle my shoes with care?

Most of the answers to the above question are more opinion than science...and maybe that is the best we are going to do.  UNLESS we try some big experiments.  What if everyone in Kansas went back to work wearing masks but Iowa went back without masks.  Keep everything else the same.  Then collect the data??

Yinon Weiss did an interesting analysis of death outcomes in various states based on when they implemented the stay-at-home order. (This piece of data is the same one used by IHME in their models that predicted the height of the death curve.) Weiss' analysis showed no correlation between when a state implemented the stay-at-home order and the number of deaths per capita 21 days into their epidemic. Early implementation of stay-at-home has been used to explain the low death rate in California, but it doesn't explain many other entities with low death rates that even to this date have not issued stay-at-home orders. The graph is below, but I suggest you go to the article for the full explanation.

Yinon Weiss Analysis