New York City may have had nearly 2 million cases of COVID-19, according to an antibody study that revealed that 21% of tested NYC residents has had the virus, according to the New York Times.

The information comes from testing done on 1,300 supermarket shoppers in New York City this week, and the results were announced Thursday by New York Gov. Andrew Cuomo.

"What does it mean? I don't know," Cuomo said during his daily press briefing. "These are people who were out and about shopping. They were not people who were in their homes, they were not people who were isolated, they were not people who were quarantined."

The numbers: The study had a sample size of 1,300 people in New York City. Of those, 21% tested positive for COVID-19 antibodies. If that percentage held true through the entire population, that would amount to approximately 1.7 million cases — far more than the current count.

The statewide study tested 3,000 people total in the state, and the percentage of people in that sample that tested positive was 14%, which would amount to 2.6 million cases if applied to the entire population. The current number of total cases in New York is about 250,000.

If those numbers are accurate, the infection mortality rate in New York would be about 0.5% Cuomo said.

Are the numbers reliable? Some experts have reservations about the accuracy of antibody tests right now, including Dr. Demetre C. Daskalakis, one of NYC's top disease control officials. From NYT:

Hours before Mr. Cuomo's presentation, a top New York City health official cautioned against making too much of the usefulness of the test results in making critical decisions about social distancing and reopening the economy, particularly in identifying immunity.



The city's top disease control officials, Dr. Demetre C. Daskalakis, wrote in an email alert on Wednesday that the tests "may produce false negative or false positive results," pointing to "significant voids" in using the science to pinpoint immunity.