On Sunday, July 12th, New York City's Department of Health reported zero COVID-19 deaths — this was at least the second time this was declared since the virus swept through the city earlier this year, and ostensibly meant that no one died from the virus the day before, Saturday July 11th. The feel-good headline of the pandemic — which was trending on Twitter and was not 100% accurate — had New Yorkers celebrating, but what does "zero deaths" really mean? As with all things Covid, it's complicated.

Here's how that number came to be. Each death is assigned a date, based on when the death certificate came in. On Sunday, it was announced that the total of all COVID-19 deaths went up by 5, but since all of the deaths were assigned dates in the past, that meant zero deaths were recorded for Saturday. For now. Over the next week, it is likely that more deaths will be assigned to Saturday, July 11th. Additionally, death numbers are tallied separately by the City and the State Departments of Health, so to truly report there were zero deaths, both agencies would have to agree on that number, and that number would have to be finalized and unchanged for at least one week, and possibly much longer, before we could absolutely say with certainty that "officially" no one died of COVID-19 on that day.

The zero deaths, even if not accurate, is still important, because it signals that numbers are genuinely on the decline. If this trend continues, eventually there may be days, when all the numbers are totaled, where the number remains zero.

However, over the past week, there have been, on average, 12 confirmed deaths and 1 probable death each day, meaning it's very unlikely that we just saw a true zero death day. This has happened before: on June 4th, New York City reported zero deaths, but looking back at that date now, with the data we have a month later, the true number has risen to 32 confirmed and 5 probable deaths.

It is likely this pattern will repeat several more times, as we get closer to zero actual deaths, so treat any similar declarations by reporters or people on social media with caution.

Update, July 13th, 1 p.m.: On Monday afternoon, the city updated the deaths by date file. There are still zero confirmed deaths on Saturday, but already 3 probables added. These numbers will likely go up over the next week.

Update, July 14th: The city is now reporting four confirmed deaths on July 11th.