In the spring, at the peak of the pandemic, about one out of five people who tested positive ended up in the hospital. According to the latest city figures, it's now closer to around one in ten. Columbia University epidemiologist Dr. Jessica Justman said that's surprisingly low. The data don't give a clear explanation why, she said, but it could be that a much higher proportion of positives now are people who are young and healthy, compared to those in the spring.

"My first guess is that people who are vulnerable are being more careful," Justman said.

She said another reason could be that those who are getting infected are being exposed to lower doses of coronavirus, because they're wearing masks and social distancing.