Core Viewpoint - The flu positivity rate among outpatient cases has approached 45%, indicating a significant prevalence of flu-like symptoms, but this does not mean that 45% of the general population is infected with the flu [1][3]. Group 1: Flu Positivity Rate and Symptoms - The flu-like cases refer to patients with respiratory symptoms such as fever and cough who visit outpatient services, and the positivity rate is derived from testing these specific cases [1]. - Among those with flu-like symptoms, the positivity rate for H1N1 (swine flu) exceeds 40%, while over 50% of cases are attributed to other pathogens like rhinovirus and respiratory syncytial virus [3][5]. Group 2: Symptoms in Different Age Groups - In younger populations, symptoms include significant fatigue and muscle aches, with high fever (38°C to 39°C) being common, while sore throat and cough are less pronounced [5]. - Children often experience high fever lasting several days, while elderly patients may not exhibit high fever but have a higher incidence of pneumonia, which can be overlooked [5][8]. Group 3: High-Risk Groups and Treatment - Individuals aged 65 and older are identified as a high-risk group for flu, and early diagnosis and treatment are emphasized to reduce severe outcomes [7][8]. - Antiviral medications should be administered within 48 hours of symptom onset to lower the risk of severe illness [8]. Group 4: Vaccine Efficacy and Infection - Flu vaccines are updated annually based on predictions from the World Health Organization, with effectiveness ranging from 30% to over 60% depending on the accuracy of the predictions [10]. - Even if vaccinated individuals contract the flu, the severity of the illness is generally reduced, and antiviral medications can still be beneficial [11][13].