The incubation period refers to the time from when pathogenic microorganisms invade the human body to when symptoms appear. We call this the incubation period. The duration of the incubation period is related to the patient's resistance and the virulence of the pathogenic microorganisms. Generally speaking, the incubation period for influenza A is usually about 2-4 days, while for other types like influenza B and C, the incubation period can often reach 5-7 days. During the incubation period of influenza, patients often do not exhibit typical flu symptoms such as coughing, sore throat, and fever. The primary manifestations may be general malaise, such as muscle and skeletal pain, loss of appetite, poor digestion, abdominal pain, and diarrhea. Therefore, it is very easy to misdiagnose these symptoms as other diseases during the incubation period.