Nassau settles down, Brooklyn… getting there?
Around August 31, Covid-19 cases in Nassau county started to diverge, sharply upwards, from New York City and Westchester county. The graphic below is a daily count of new cases per 100,000 population, not a rolling average. About three weeks later, starting around September 19, it appears Nassau county once again moved back into sync with the broader NYC area. How much of the entire Nassau spike is localized in the Hofstra University town of West Hempstead? Did it start off mini-spikes in surrounding towns? The data reported to the public by NY State is at the county level, so the answer to that question is known only to the county officials and NY state. But the main point worth noting is Nassau county appears to be in sync with NYC and Westchester for the past 10 days, suggesting they are meeting Gov. Cuomo’s metrics for not being named-and-shamed.
Looking at the five NYC boroughs/counties, the spike in Brooklyn starting around September 16 is clearly ongoing. If using Nassau county as a benchmark, the Brooklyn spike can be expected to revert to status quo ante around the first week of October. But that is speculative. The time needed to regain control over transmission depends entirely on how localized the Brooklyn spike is — how event-specific or locale-specific the spike is. With Nassau county, it started with an event, the reopening of a university; and a locale, the town in which the university was located. Making it easier to tamp down the break out. If the Brooklyn spike cannot be similarly localized, the solution may take longer to implement.