1128. Clinical Features and Outcomes of Medically-Attended Influenza in Community-Dwelling Older Adults
Session: Poster Abstract Session: Influenza and H1N1 Diagnosis, Epidemiology, and Viral Outcome
Saturday, October 22, 2011
Room: Poster Hall B1
  • 75+_IDSA_09212011_FINAL.pdf (171.8 kB)
  • Background: 

    Clinical features and outcomes of influenza have not been well characterized for infections among adults ≥75 years of age identified using highly sensitive and specific diagnostic tests.


    Individuals were prospectively enrolled and tested for influenza after a medical encounter for acute respiratory illness.  Influenza was confirmed by rRT-PCR during four influenza seasons (2005-06 through 2008-09); viral culture was used in 2004-05. Illness characteristics were obtained via interview. Antiviral treatment, pneumonia diagnoses, and hospital admissions were collected from electronic medical records. Clinical features and illness outcomes among influenza cases aged ≥75 years were compared to test negative controls of the same age and to influenza cases aged 60-74 years.


    We enrolled 313 adults aged ≥75 years (older group) and 598 adults aged 60-74 (younger group). Influenza was detected in 56 (18%) of the older group and 136 (23%) of the younger group (p=0.09); influenza A accounted for 89% and 69% of infections, respectively. Among those subtyped, influenza A(H3N2) accounted for 100% of type A infections in the older group and 94% in the younger group (p=0.30). Symptoms were similar in both age groups, but older adults were less likely to report a fever (61% vs. 77%, p=0.04). Within 30 days of illness onset, 23% of older influenza cases were admitted to a hospital, compared to 16% of younger influenza cases (p=0.25) and 25% of test negative controls ≥75 years (p=0.84); 33% of influenza cases with chronic lung disease were hospitalized, compared to 14% of cases without (p=0.003). The median age was 71 years for hospitalized cases and 70 years for cases not hospitalized (p=0.03). Influenza antiviral prescriptions were given to 11% and 13% of older and younger influenza cases, respectively. Among the older influenza cases, the median interval from illness onset to clinical encounter was the same for those who did and did not receive an antiviral drug (3 days; p=0.26).


    In this small population of community-dwelling older adults, hospitalization was common following influenza or other medically attended respiratory illness. Chronic lung disease was associated with increased risk of hospitalization among influenza cases.

    Subject Category: V. Virology including clinical and basic studies of viral infections, including hepatitis

    Stephanie Irving, MHS, Epidemiology Research Center, Marshfield Clinic Research Foundation, Marshfield, WI, David K. Shay, MD, MPH, Centers for Disease Control and Prevention, Atlanta, GA and Edward Belongia, MD, Marshfield Clinic Research Foundation, Epidemiology Research Center, Marshfield , WI


    S. Irving, None

    D. K. Shay, None

    E. Belongia, None

    Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.