First wave of the influenza A/H1N1v pandemic in Switzerland.

AIM: To describe the disease burden, clinical pattern and outcome of influenza-related cases presenting to a Swiss Emergency Department (ED), during the first wave of the 2009 pandemic.

METHODS

Retrospective analysis of prospectively collected data at the University Hospital of Basel, Switzerland. All patients presenting to the ED with influenza-like symptoms from June 1 to October 23, 2009, were studied. Rate of hospitalisation, demographic characteristics, symptoms, microbiological diagnoses and complications of influenza infection were analysed.

RESULTS

One tenth (808 of 8356 patients) of all non-trauma ED presentations, during the study period, were a result of suspected influenza-related illness. Influenza A/H1N1v infection accounted for 5% of these presentations. Patients aged 50 years or less accounted for 87% of these presentations and for 100% of A/H1N1v infection. The highest detection rate of A/H1N1v-infection occurred in July, and the highest rate of clinical presentations occurred in August 2009. Underlying medical disease was observed in 14% of all patients. The presence of fever, cough and myalgia was the prime clinical predictor for the presence of A/H1N1v infection. 16% of patients with this triad suffered from A/H1N1v.

CONCLUSION

Suspected A/H1N1v infection contributed to a considerable health care burden in Switzerland. However, the rate of true positivity was low (5%), hospitalisations rare (5%), and mortality did not occur. Therefore, the first wave of the A/H1N1v pandemic in Switzerland was rather media "hype" than real threat.