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Longer hospitalization likely with hospital-onset flu vs. community-onset cases
Patients with hospital-onset influenza stayed in the hospital longer and were more likely to be in the ICU than those with community-onset influenza, according to CDC researchers.
“Seasonal influenza is responsible for more than 200,000 hospitalizations and between 3,000 and 49,000 deaths each year in the United States, and poses important infection control risks and challenges to both patients and health care personnel,” they wrote in the American Journal of Infection Control. “Although hospital-onset influenza contributes to morbidity and mortality among hospitalized patients, little is known about its overall epidemiology.”
Using data from the 2010-2011 influenza season that was collected through the Influenza Hospitalization Surveillance Network, the researchers determined the incidence of hospital-onset influenza. A community-onset case of influenza was defined as confirmation of influenza infection within 3 days of hospital admission. Hospital-onset cases were defined as those who developed fever or respiratory illness with a confirmed influenza diagnosis more than 3 days after admission for non-respiratory illness.
Among 6,171 cases reported to the surveillance network during the season, 172 (2.8%) were classified as hospital-onset cases, 5,912 (96%) were classified as community-onset and the remaining 87 cases were indeterminate. Among the hospital-onset cases, the median age was 55 years and 84% were aged at least 18 years. Ninety percent had one chronic medical condition, such as cardiovascular disease (40%), asthma or lung disease (40%), or metabolic disease (39%). In comparison, only 78% of community-onset cases had one or more chronic medical conditions.
Among the hospital-onset cases, the median length of hospital stay after influenza diagnosis was 7.5 days, significantly longer than the 3-day median stay for those with community-onset influenza. Seventy-two hospital-onset cases (42%) were admitted to the ICU, of which 46 (27%) required mechanical ventilation. In comparison, 1,021 (17%) of community-onset cases were admitted to the ICU and 465 (7.9%) required mechanical ventilation. Lastly, 16% of hospital-onset cases died during hospitalization vs. 2.9% of community-onset cases.
“Whether or not [hospital-onset] influenza leads directly to poor outcomes among hospitalized patients merits further investigation in a more comprehensive study that can evaluate the relative risk of severe outcomes associated with influenza in [hospital-onset] compared with [community-onset] cases,” the researchers wrote. “Physicians should be aware of influenza as a potential [hospital-onset] infection during influenza season and of the possibility of severe illness, particularly among patients at increased risk for complications from influenza.”
Disclosure: The researchers report no relevant financial disclosures.