During the 1918 H1N1 influenza pandemic, there were approximately 50 million influenza-related deaths worldwide, including 675 000 in the US. Few persons in the US have a frame of reference for the historic levels of excess mortality currently being observed during the coronavirus disease 2019 (COVID-19) pandemic. In this study by Faust, et al. (2020), excess deaths in New York City during the peak of the 1918 H1N1 influenza pandemic were compared with those during the initial period of the COVID-19 outbreak.

This cohort study compared the incident rates of all-cause mortality in New York City during the peak of the 1918 H1N1 influenza pandemic and the early COVID-19 outbreak in 2020 using public data from the Centers for Disease Control and Prevention (1914-1918), The New York City Department of Health and Mental Hygiene (2020), and the US Census Bureau (2017-2020). This study was deemed to be exempt from institutional review approval because it used publicly available data. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.

Analyses were performed using SAS, version 9.4 (SAS Institute). Incidence rate per person-months and corresponding 95% CIs were calculated for October and November (61 days) from 1914 through 1918, and for March 11, 2020, through May 11, 2020 (61 days), separately. Sixty-one day incident rates were divided by 2 to obtain person-month units. To compare the all-cause mortality between 2020 and 2019, an incidence rate ratio and its corresponding 95% CI was calculated.

During the peak of the 1918 H1N1 influenza outbreak in New York City, a total of 31 589 all-cause deaths occurred among 5 500 000 residents, yielding an incident rate of 287.17 deaths per 100 000 person-months (95% CI, 282.71-291.69 deaths per 100 000 person-months). The incident rate ratio for all-cause mortality during the H1N1 influenza pandemic compared with corresponding periods from 1914 to 1917 was 2.80 (95% CI, 2.74-2.86). During the early period of the COVID-19 outbreak in New York City, 33 465 all-cause deaths occurred among 8 280 000 residents, yielding an incident rate of 202.08 deaths per 100 000 person-months (95% CI, 199.03-205.17 deaths per 100 000 person-months). The incident rate ratio for all-cause mortality during the study period of 2020 compared with corresponding periods from 2017 through 2019 was 4.15 (95% CI, 4.05-4.24). The incident rate ratio for all-cause mortality during the peak of the 1918 H1N1 influenza pandemic and the early 2020 COVID-19 outbreak was 0.70 (95% CI, 0.69-0.72).

Reference: Faust JS, et al. Comparison of Estimated Excess Deaths in New York City During the COVID-19 and 1918 Influenza Pandemics. JAMA Netw Open. 2020;3(8):e2017527. doi:10.1001/jamanetworkopen.2020.17527