How New York went from a COVID epicenter to having one of the nation's lowest positivity rates

Gov. Andrew Cuomo on Monday announced that New York’s seven-day average of COVID-19 positivity rates was 0.5%—the state's lowest since it began testing in March 2020. According to Johns Hopkins University data, that ties New York with Massachusetts in having the lowest positivity rate in the nation.

The state has come a long way. In January, Mount Sinai Health System was recording about a 10% positivity rate among its patients, said Dr. David Reich, president of Mount Sinai Hospital. That same month, when Northwell Health’s COVID-19 testing labs were in full force, running 16,000 tests per day during the second surge, its positivity rate was about 12%. Dr. John D’Angelo, senior vice president and executive director of emergency medicine services at Northwell, said it was hard to assess the true rate of the first surge last spring, as tests were limited back then.

Positivity rates have fallen since January because of a combination of factors, said Anna Bershteyn, assistant professor in the population health department at the NYU Grossman School of Medicine.

Part of the reason is seasonality, all three experts agreed. Although it’s not clear why, coronaviruses including COVID-19 do not spread as quickly in warmer weather.

In the summer, positivity rates fell after a surge, although rates were still higher back then than they are now, Bershteyn said.

The strong push for COVID-19 vaccines since they became available in December has been another key factor, D’Angelo said. With the state moving closer to herd immunity, including people who developed antibodies from a previous COVID-19 infection, it is little wonder New York’s rate fell precipitously this month, he said.

Cuomo announced in his briefing that 68.6% of New York adults have received at least one dose of a vaccine, and 59.5% of that group have completed their vaccine series. Including all age groups, 56.6% have received at least one dose, and 47.9% have been fully vaccinated, the governor said. Cuomo and other state leaders said they expect New York to hit the 70% threshold—typically pegged as a minimum for herd immunity—as soon as next week, if not by the first week of July.

There are concerns, however, that the state’s halcyon days of low virus spread might not last.

“We’ve had the luxury of virtually no flu last year, but it’s going to return before COVID will be completely gone,” D’Angelo said.

It remains to be seen what the severity of a combined flu and COVID-19 season looks like, he added.

Health experts continue to exalt that testing should be emphasized even amid low positivity rates, because detected cases could be identified and quarantined more effectively, Reich said. Data has shown that rigorous testing correlates to lower COVID rates, he added.

Johns Hopkins data shows that New York had a testing rate of 560 per 100,000 individuals, the second highest after Rhode Island. Alabama, which had one of the lowest testing rates, 47.3 tests per 100,000 people, also had the nation’s highest COVID-19 positivity rate: 13.5%.

“Especially with schoolchildren who have yet to be able to take the vaccine, we need to ensure that mass screenings and some sensible precautions, such as mask wearing in certain situations, remain in place,” Reich said.