Quantifying influenza exposure within California hospitals and nursing homes using administrative data.

Influenza acquisition occurs in hospitals and nursing homes (NHs), highlighting the need for infection prevention. We used administrative data to quantify influenza exposure and facility-onset influenza rates for California hospitals and NHs during the 2015-2016 influenza season. Higher facility-onset influenza rates were identified in NHs compared with hospitals, despite fewer influenza exposure-days in NHs. Validation of administrative data are needed.