A positive rate of 3% in coronavirus tests is a critical threshold for New York. That’s when the mayor closed public schools last week. The governor says a sustained level of 3 percent in the city will result in a ban on indoor dining, the closure of gymnasiums and barber shops, and capping 25 people on attendance at places of worship, even as the holidays approach.
But as important as that 3% rate is, it seems the city and state can’t agree on whether it’s been reached.
This conflict unfolded over the past week, with Mayor Bill de Blasio claiming 3% had been violated, while Governor Andrew M. Cuomo said the rate of positive tests was much lower than that. Each relies on its own statistics, which are compiled and reported in different ways. And it turns out that the state and the city can’t agree on which tests to include in the calculation, either.
The gap can be striking: On Saturday, for example, the city said its seven-day average was 3.11%. Mr. Cuomo’s office, however, put the city’s rate more than half a point lower, at 2.54%.
It’s the latest jarring post between two rivals that unfolded throughout the pandemic, adding a level of dysfunction and confusion to the response.
The cause of the deviation lies both in the tests included and in the time frame in which the statistics are reported. The state considers a new case to arise on the day the test result arrives. The city dates each new case at the time the sample was provided.
So if an infected person is tested on Monday and the result is reported to health officials on Wednesday, the state would include the positive test in Wednesday’s tally of new cases, while the city would add it to Monday’s column.
Since the 3% threshold is based on a seven-day moving average, it is important to know which day a new case is recorded.
Another factor is that antigen tests, although generally faster, are less likely to detect infection in people with a low viral load. New York State includes antigen test results in its official measurements. The city does not. It is based solely on the more sensitive test known as the polymerase chain reaction. That’s why the state – which counts both antigen and PCR testing – may have a higher number of overall cases in New York City, but a lower percentage of positives.