Comparison of Influenza Epidemiological and Virological Characteristics between Outpatients and Inpatients in Zhejiang Province, China, March 2011-June 2015.

Feng Ling,Enfu Chen,Shelan Liu,Xiaoxiao Wang,Zhao Yu,Xueying Zhang,Jian Cai,Wei Cheng

doi:10.3390/ijerph14020217

Abstract

Given the rapid rate of global spread and consequently healthcare costs related to influenza, surveillance plays an important role in monitoring the emerging pandemics in China. However, the characteristics of influenza in Southeast of China haven’t been fully studied. Our study use the surveillance data collected from 16 sentinel hospitals across Zhejiang Province during March 2011 through June 2015, including the demographic information and respiratory specimens from influenza-like illness (ILI) patients and severe acute respiratory illness (SARI) patients. As analysis results, most SARI and ILI patients were in the age group of 0–4 years old (62.38% of ILI and 71.54% of SARI). The respiratory specimens have statistically significantly higher positive rate for influenza among ILI patients than that among SARI patients (p < 0.001). The comparison between ILI patients and SARI patients shows no statistically significantly difference in detecting influenza virus type and influenza A virus subtype. The SARI and ILI patients were found to be positively correlated for overall positive rate (r = 0.63, p < 0.001), the weekly percentage of A(H1N1)pdm09 (r = 0.51, p < 0.001), influenza B virus (r = 0.17, p = 0.013), and A/H3N2 (r = 0.43, p < 0.001) among all the positive numbers. Our study demonstrated that the activities of influenza virus, including its subtypes, had a similar temporal pattern between ILI and SARI cases.

Highlights

Influenza virus is estimated to cause 3 to 5 million cases of severe illness and 250,000 to500,000 deaths each year, while 5%–10% of adults and 20%–30% of children are infected with the influenza virus worldwide [1]
Spearman correlation was applied to analyze the linear relationship of the influenza virus positive rate, weekly percentage of influenza virus subtypes accounted for all the positive numbers between severe acute respiratory illness (SARI) and influenza-like illness (ILI) patients
We found that the weekly percentage of influenza virus types/subtypes among all the identified influenza cases were significantly correlated between SARI and ILI patients, with A(H1N1)pdm09 (r = 0.51, p < 0.001), influenza B virus (r = 0.17, p = 0.013), and A(H3N2) (r = 0.43, p < 0.001) (Table 3)

Summary

Introduction

Influenza virus is estimated to cause 3 to 5 million cases of severe illness and 250,000 to. 500,000 deaths each year, while 5%–10% of adults and 20%–30% of children are infected with the influenza virus worldwide [1]. In lower and middle-income countries, influenza could result in large economic burden encompassing direct costs to the health service and households, and indirect costs of productivity losses [2,3]. Vaccination is a cost-effective way to reduce the public health and economic impacts caused by influenza. Because of the antigenic shift and drift of the virus, the influenza vaccine composition needs regular updates. The selection of strains for the annual influenza vaccine are primarily. Res. Public Health 2017, 14, 217; doi:10.3390/ijerph14020217 www.mdpi.com/journal/ijerph

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Discussion

Conclusion