Hospital-acquired influenza in the United States, FluSurv-NET, 2011–2012 through 2018–2019

Abstract

Objective: To estimate population-based rates and to describe clinical characteristics of hospital-acquired (HA) influenza. Design: Cross-sectional study. Setting: US Influenza Hospitalization Surveillance Network (FluSurv-NET) during 2011–2012 through 2018–2019 seasons. Methods: Patients were identified through provider-initiated or facility-based testing. HA influenza was defined as a positive influenza test date and respiratory symptom onset >3 days after admission. Patients with positive test date >3 days after admission but missing respiratory symptom onset date were classified as possible HA influenza. Results: Among 94,158 influenza-associated hospitalizations, 353 (0.4%) had HA influenza. The overall adjusted rate of HA influenza was 0.4 per 100,000 persons. Among HA influenza cases, 50.7% were 65 years of age or older, and 52.0% of children and 95.7% of adults had underlying conditions; 44.9% overall had received influenza vaccine prior to hospitalization. Overall, 34.5% of HA cases received ICU care during hospitalization, 19.8% required mechanical ventilation, and 6.7% died. After including possible HA cases, prevalence among all influenza-associated hospitalizations increased to 1.3% and the adjusted rate increased to 1.5 per 100,000 persons. Conclusions: Over 8 seasons, rates of HA influenza were low but were likely underestimated because testing was not systematic. A high proportion of patients with HA influenza were unvaccinated and had severe outcomes. Annual influenza vaccination and implementation of robust hospital infection control measures may help to prevent HA influenza and its impacts on patient outcomes and the healthcare system.

Drug use and severe outcomes among adults hospitalized with influenza, 2016–2019

“…FluSurv‐NET conducts population‐based surveillance for laboratory‐confirmed, influenza‐associated hospitalizations through a network of acute care hospitals in catchment areas in states participating in the Emerging Infections Program (EIP) or the Council of State and Territorial Epidemiologists (CSTE) Influenza Hospitalization Surveillance Project 17–19 . EIP states include California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon, and Tennessee while CSTE states include Michigan, Ohio, and Utah.…”

“…Cases with a positive influenza test >3 days after hospital admission were excluded from the analysis. Influenza testing is clinician‐driven and influenza testing practices vary across the hospitals participating in FluSurv‐NET 17,20 . Information on over 400 variables of interest including substance use, demographics, risk and behavioral factors, and significant health outcomes are collected via retrospective medical record reviews by trained surveillance officers using a standardized case report form.…”

“…Complete medical record abstractions were conducted for all patients younger than 50 years and all patients of any age who died during their hospitalization. Of the 14 surveillance sites included during these two seasons, seven opted to implement a sampling strategy during the 2017–2018 season and six used the sampling strategy during the 2018–2019 season 17,19 . Current season influenza vaccination was obtained using up to four potential sources (medical record review, state immunization registry, primary care provider or pharmacy inquiry, or through case or proxy interview) and defined as a record of vaccine receipt at least 2 weeks prior to the positive influenza test associated with hospital admission.…”

“…These models compared PWUD with specific drug use with non‐PWUD and controlled for the same variables as the general drug use models. All analyses were conducted using SAS 9.4 24 and accounted for the complex survey design using methods previously described 17–20 …”

“…FluSurv‐NET conducts population‐based surveillance for laboratory‐confirmed, influenza‐associated hospitalizations through a network of acute care hospitals in catchment areas in states participating in the Emerging Infections Program (EIP) or the Council of State and Territorial Epidemiologists (CSTE) Influenza Hospitalization Surveillance Project. 17 , 18 , 19 EIP states include California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon, and Tennessee while CSTE states include Michigan, Ohio, and Utah. Cases are defined as a catchment area resident admitted to a hospital with a positive influenza test within 14 days prior to or during their hospitalization, with admission date between October 1 and April 30 annually; cases can include catchment area residents admitted to hospitals outside the catchment area.…”