Shok Yin Lee
Department of Medicine, Eastern Health, Victoria, Australia 


Comparison of incidence of Influenza cases between year 2014 and 2015 in a Victorian Hospital
Shok Yin Lee1, Mae Chyi Tan1, Ceyda Gayde2, Emily Shen1
Department of General Medicine, Eastern Health, Victoria, Australia
2Department of Geriatrics, Eastern Health, Victoria, Australia

Background: In year 2015, the double strain change from 2014 Influenza vaccine caused a one-month delay in the commencement of National Seasonal Influenza Immunisation Program in Australia. There was, not only, an increase in the number and severity of Influenza cases in year 2015, but also no bimodal age distribution trend as seen in previous years. 

Objective: To compare the incidence of Influenza rates, strains and severity in year 2015 with year 2014.

Method: This is a retrospective analysis of all patients who were admitted with respiratory tract infection between May 2015 and September 2015 under Department of General Medicine in a Victorian tertiary center hospital. All patients above 18 years were included. Rates of confirmed influenza cases were analyzed and compared with year 2014.

Result: Total number of influenza cases in year 2015 was 53. 53% of them had Influenza vaccination prior compared to 23% in 2014. 66% (35/53) of them had confirmed Influenza A compared to 18 patients with Influenza B. 5.6% developed severe infections and one patient had to be palliated. In comparison, there were only a total of 13 patients with confirmed Influenza in year 2014 and 12/13 (92%) were Influenza A. None of them had severe infections. There was no significant difference between age and gender characteristics between these two groups. In terms of comorbidities, 24.5% patients with Influenza in 2015 have underlying lung disease compared to only 7.6% in 2014.

Conclusion: The incidence of Influenza cases in 2015 increases four-fold in comparison to year 2014 with the Influenza B virus seen as a new rising Influenza strain.