Increased emergency department chief complaints of fever identified the influenza (H1N1) pandemic before outpatient symptom surveillance

Abstract

Objective: To determine whether a sentinel clinic network or an emergency department (ED) was more timely in identifying the 2009 influenza A (H1N1) pandemic.

Methods: All reasons for presenting to the adult regional medical ED were coded online by admission secretaries, without the aid of medical personnel. Increased influenza activity defined by weekly chief complaints of fever was compared with activity defined by the Israel Center for Disease Control (viral surveillance as well as a large sentinel clinic network).

Results: Influenza activity during the pandemic increased in the ED 2 weeks before outpatient sentinel clinics. During the pandemic, maximal ED activity was much higher than in previous seasons. Maximal activity during the past 5 years correlated with the timeliness of the chief complaint of fever in identifying the onset of epidemics.

Conclusion: Chief complaint of fever in the ED can be a sensitive marker of increased influenza activity and might replace the use of sentinel clinics.

Fig. 1

Increased frequency of fever complaints during week 24 in the ED (rate is number per week), 2 weeks before an increase of influenza-like symptoms seen in the sentinel clinics (rate is number per 100,000). Areas under thick straight lines represent background activity