My mobile phone number is bound to my brother's health code, and then my health code turns yellow, so does his.

It should be to the high-risk area, and then your code didn't turn yellow in time, and the child's code changed first.

Do a nucleic acid test, and it will turn into a green code if there is no problem.

The substance of nucleic 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 the gold standard for the diagnosis of novel coronavirus infection.