Influenza viruses are categorized into influenza A virus, influenza B virus, and influenza C virus. To determine whether a patient is infected with influenza virus through virus testing, a negative test generally means that the patient is not infected with the virus, while a positive test means that the patient is infected with the influenza virus. Some patients may not show clinical symptoms immediately after being infected with influenza virus, and may recover spontaneously due to their own immunity. However, for people with poor immunity, if they are positive for influenza virus, they should intervene as soon as possible to treat the symptoms with antiviral drugs.