"The first seropositive samples in our study were already detected during the week of 23 February, one week before the first confirmed case of SARS-CoV-2 in NYC was identified, which suggests that SARS-CoV-2 was probably introduced to the NYC area several weeks earlier than has previously been assumed. This would not be unexpected given the unique diversity and connectivity of NYC and the large numbers of travellers that were arriving from SARS-CoV-2-affected regions of the world in January and February 2020. The antibody titres of initial positive individuals were low, which is consistent with slower seroconversion of perhaps mild cases. Of course, we cannot exclude with absolute certainty that some of the lower positive titres are false positives as the initially low seroprevalence falls within the confidence intervals of the positive predictive value. Of note, the seroprevalence in the routine care group (as well as the urgent care group at the end of May, after the peak) falls significantly below the threshold for potential community immunity, which has been estimated by one study to require at least a seropositivity rate of 67% for SARS-CoV-24. On the basis of the population of NYC (8.4 million), we estimate that by the week ending 24 May, approximately 1.7 million individuals had been infected with SARS-CoV-2. Taking into account the cumulative number of deaths in the city by 19 May (16,674—this number includes only officially confirmed, not suspected, COVID-19-related deaths), this suggests a preliminary infection fatality rate of 0.97% (with the assumption that both seroconversion and death occur with similar delays). This is in stark contrast to the infection fatality rate of the 2009 H1N1 pandemic, which was estimated to be 0.01–0.001%."