2317. Excess Influenza-Attributable Mortality in Los Angeles County (LAC) for the 2013–2014 Through 2017–2018 Seasons

Abstract Background Deaths caused by seasonal influenza are impossible to measure directly and are typically estimated using statistical models. We applied a previously developed model to Los Angeles County (LAC) data for the 2013–2014 through 2017–2018 influenza seasons. Methods Excess deaths attributable to influenza were estimated using a negative binomial regression model incorporating laboratory surveillance data and weekly counts of deaths with an underlying respiratory or circulatory cause of death. We obtained death data from the National Vital Statistics System. Population estimates for LAC were prepared by Hedderson Demographic Services for LAC Internal Services Department. The weekly total number of respiratory specimens tested and number positive for influenza or respiratory syncytial virus were provided by nine healthcare systems in LAC. Influenza-associated deaths in all ages are reportable to LAC Department of Public Health; confirmed reports are counted as observed deaths. Results The midyear LAC population increased from 10,019,362 in 2013 to 10,272,648 in 2017. The median number of observed influenza deaths reported to public health was 81 in 2015–2016 (minimum [min]: 56 in 2015–2015, maximum [max]: 288 in 2017–2018). The median number of seasonal deaths with an underlying respiratory or circulatory cause was 27,455 (min: 25,828, max: 28,732). The median estimate of influenza-attributable deaths was 1,478 (95% confidence interval [CI]: 823–2,613) in 2015–2016, with a min of 1,045 deaths (CI: 629–2,258) in 2013–2014 and a max of 1,905 (CI: 1,075–3,269) in 2017–2018. Conclusion Although influenza-associated deaths at all ages are reportable in LAC, a variety of barriers to reporting exist. Our estimates indicate that influenza-associated deaths in LAC are underreported. The more comprehensive modeled estimate of the burden of influenza can better inform local policy and planning decisions. Disclosures All authors: No reported disclosures.