The substance of acid detection is the nucleic acid of virus.
Nucleic acid detection is to determine whether the patient is infected by COVID-19 by detecting whether there is nucleic acid of foreign invasive virus in respiratory tract samples, blood or feces. Therefore, once the nucleic acid is "positive", it can prove that there is a virus in the patient.
After COVID-19 infects the human body, it will first reproduce in the respiratory system, so we can judge whether the human body is infected with the virus by detecting the virus nucleic acid in sputum and nasopharyngeal swab. Therefore, positive nucleic acid detection can be used as a new standard for the diagnosis of novel coronavirus infection.
There are several reasons why the health code turns red: 1. I travel across provinces and cities with my mobile phone, especially to some places with serious epidemics. 2. When the mobile phone is turned on, it passes through different provinces and cities. 3. Drive to different provinces and cities by mobile phone. 4. Mobile phone GPS positioning error, such as the positioning error at the junction of two provinces, but this situation is rare.