What does it mean to have a nucleic acid test 48 hours before getting on the bus?

Nucleic acid test 48 hours before boarding the train refers to the nucleic acid test report within 48 hours before boarding the train. A negative 48-hour nucleic acid test certificate means that the nucleic acid test report is valid within 48 hours or less.

A negative 48-hour nucleic acid test proves that the nucleic acid test report is valid within 48 hours or less. If it exceeds 48 hours, a new nucleic acid test is needed. Passengers who take air tickets, train tickets or bus tickets must be tested for nucleic acids within 48 hours of departure time.

Knowledge of nucleic acid detection.

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.