Asymptomatic infected individuals usually have no clinical symptoms because they do not cause clinical morbidity and are recessive infected individuals. The infection with pathogen is only found when pathogen-related tests are done, and pathogenic tests can usually be performed by nucleic acids, antigens, and antibodies. The organism can produce a specific immune response to the pathogenic microorganism, and the infected person can also excrete the pathogenic microorganism, causing others to become infected and contagious. If a patient is in the incubation period and has not yet reached the onset of the disease, the asymptomatic infected person found by pathogenic examination at this time is not a true asymptomatic infected person, and clinical symptoms can appear after the incubation period. The symptoms that appear are the same as other onset of the disease, for different diseases, clinical symptoms differ, common infection symptoms are as follows: 1, respiratory infection symptoms: such as nasal congestion, runny nose, sore throat, dry cough, cough, shortness of breath, shortness of breath and other clinical symptoms; 2, gastrointestinal infection symptoms: can appear abdominal pain, diarrhea, nausea, vomiting and other uncomfortable symptoms; 3, cardiovascular infection symptoms: can appear Symptoms of intracranial infection: dizziness, headache, orbital radiating pain, blurred vision, irritability, etc.; 5, symptoms of urinary tract infection: frequent urination, urgent urination, painful urination, hematuria, lumbago, etc.; 6, systemic symptoms: fever, chills, muscle pain, weakness, sleepiness, lack of energy, etc.