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BackgroundRates of influenza hospitalizations differ by age, but few data are available regarding differences in laboratory-confirmed rates among adults aged ≥65 years.MethodsWe evaluated age-related differences in influenza-associated hospitalization rates, clinical presentation, and outcomes among 19 760 older adults with laboratory-confirmed influenza at 14 FluSurv-NET sites during the 2011–2012 through 2014–2015 influenza seasons using 10-year age groups.ResultsThere were large stepwise increases in the population rates of influenza hospitalization with each 10-year increase in age. Rates ranged from 101–417, 209–1264, and 562–2651 per 100 000 persons over 4 influenza seasons in patients aged 65–74 years, 75–84 years, and ≥85 years, respectively. Hospitalization rates among adults aged 75–84 years and ≥85 years were 1.4–3.0 and 2.2–6.4 times greater, respectively, than rates for adults aged 65–74 years. Among patients hospitalized with laboratory-confirmed influenza, there were age-related differences in demographics, medical histories, and symptoms and signs at presentation. Compared to hospitalized patients aged 65–74 years, patients aged ≥85 years had higher odds of pneumonia (aOR, 1.2; 95% CI, 1.0–1.3; P = .01) and in-hospital death or transfer to hospice (aOR, 2.1; 95% CI, 1.7–2.6; P < .01).ConclusionsAge-related differences in the incidence and severity of influenza hospitalizations among adults aged ≥65 years can inform prevention and treatment efforts, and data should be analyzed and reported using additional age strata.

Background Few data describe the epidemiology of influenza among adults ≥65 years old according to age strata. We evaluated age-related differences in influenza-associated hospitalization rates, clinical presentation, and outcomes among older adults at 14 FluSurv-NET sites during the 2011–2012 through 2014-2015 influenza seasons. Methods Study patients were hospitalized ≤14 days after and ≤3 days before a positive influenza test. Age strata were 65–74, 75–84, and ≥85 years old. We adjusted hospitalization rates for under detection and assessed for age-related trends in risk factors and symptoms. We used logistic regression to calculate odds ratios (OR) for pneumonia and in-hospital death adjusted for season, sex, nursing home residence, smoking, medical comorbidities, influenza vaccination, and study site. Results There were 19,760 patients, including 5,956 aged 65–74 years, 6,998 aged 75–84 years, and 6,806 aged ≥85 years. There was a stepwise increase in hospitalization rates with age (figure). Increasing age was positively associated with female sex, nursing home residence, neurologic disorder, cardiovascular and renal disease, and vaccination, and inversely associated with morbid obesity, smoking, asthma, chronic metabolic disease, and immunosuppression (P < 0.01). Among 10,548 (53.3%) patients with symptom data from 2014 to 2015, increasing age was associated with a higher prevalence of altered mental status and lower prevalence of fever, myalgias, respiratory or gastrointestinal symptoms, and headache (P ≤ 0.01). Compared with 65–74 year olds, older patients had a higher risk of pneumonia (≥85 year-olds: OR 1.2, 95% CI 1.0, 1.3, P = 0.01) and death (75–84 year olds: OR 1.4, 95% CI 1.2, 1.7, P < 0.01; ≥85 year-olds: OR 2.1, 95% CI 1.7, 2.6, P < 0.01). Conclusion There are age-related differences in the epidemiology, clinical presentation, and outcomes of older adults hospitalized with influenza. These may reflect differences in health status and healthcare provider practice patterns. Public health epidemiologists should consider using additional age strata in ≥65 year-olds when analyzing influenza surveillance data. Clinicians should be aware that influenza among the oldest adults may present atypically and that mortality is increased. Disclosures E. J. Anderson, NovaVax: Grant Investigator, Research grant. Pfizer: Grant Investigator, Research grant. AbbVie: Consultant, Consulting fee. MedImmune: Investigator, Research support. PaxVax: Investigator, Research support. Micron: Investigator, Research support. W. Schaffner, Merck: Member, Data Safety Monitoring Board, Consulting fee. Pfizer: Member, Data Safety Monitoring Board, Consulting fee. Dynavax: Consultant, Consulting fee. Seqirus: Consultant, Consulting fee. SutroVax: Consultant, Consulting fee. Shionogi: Consultant, Consulting fee.

During 2000–2011, passive surveillance for legionellosis in the United States demonstrated a 249% increase in crude incidence, although little was known about the clinical course and method of diagnosis. In 2011, a system of active, population-based surveillance for legionellosis was instituted through CDC’s Active Bacterial Core surveillance (ABCs) program. Overall disease rates were similar in both the passive and active systems, but more complete demographic information and additional clinical and laboratory data were only available from ABCs. ABCs data during 2011–2013 showed that approximately 44% of patients with legionellosis required intensive care, and 9% died. Disease incidence was higher among blacks than whites and was 10 times higher in New York than California. Laboratory data indicated a reliance on urinary antigen testing, which only detects Legionella pneumophila serogroup 1 (Lp1). ABCs data highlight the severity of the disease, the need to better understand racial and regional differences, and the need for better diagnostic testing to detect infections.