The investigators evaluate the performance of e- Ab sensor, including reproducibility, sensitivity, specificity, and cross-reaction. The potential factors which may interfere with the results would be investigated. e- Ab sensor threshold decisions must maximize its sensitivity. Therefore, the threshold value in the test group is to find the decision could have 90% sensitivity and 90% specificity. With such technique, the investigators hope to make early diagnosis and give influenza patients early treatment to reduce the complications and case-fatality rate.