Should Shanghai be isolated from Xiayi?

Shanghai needs to be quarantined 14 days to return to Xiayi, and health monitoring will continue for 7 days after the expiration of centralized quarantine 14 days.

Extended data:

Nucleic acid detection method

Detection principle

All living things contain nucleic acids, including DNA and RNA. Novel coronavirus is a virus containing only RNA, and the specific RNA sequence in the virus is a sign to distinguish the virus from other pathogens. After the appearance of novel coronavirus, Chinese scientists completed the analysis of the whole genome sequence of novel coronavirus in a very short time, and found the specific nucleic acid sequence in novel coronavirus by comparing with the genome sequences of other species. If novel coronavirus's specific nucleic acid sequence can be detected in patients' samples during clinical laboratory testing, it should be suggested that patients may be infected by novel coronavirus.

2 COVID-19 detection

Principle of novel coronavirus nucleic acid detection

The most commonly used method for detecting novel coronavirus-specific sequences is fluorescence quantitative PCR (polymerase chain reaction). Because the template of PCR reaction is only DNA, novel coronavirus nucleic acid (RNA) should be reverse transcribed into DNA before PCR reaction. In the PCR reaction system, there are a pair of specific primers and a Taqman probe. The Taqman probe is a specific oligonucleotide sequence, and both ends of the probe are marked with a reporter fluorescence group and a quenching fluorescence group respectively. When the probe is intact, the fluorescence signal emitted by the reporter group is absorbed by the quenching group; If the target sequence exists in the reaction system, the probe will bind to the template during the PCR reaction, and DNA polymerase will digest the probe along the template by using the nucleic acid exonuclease activity of the enzyme, and the reporter group will be separated from the quenching group to emit fluorescence. Every time a DNA strand is amplified, a fluorescent molecule is produced. The fluorescence quantitative PCR instrument can monitor that the number of cycles (Ct value) of fluorescence reaching the preset threshold is related to the concentration of viral nucleic acid. The higher the concentration of viral nucleic acid, the smaller the Ct value. The products of different manufacturers will determine the positive judgment value of this product according to the performance of their own products.

Detection method of nucleic acid in novel coronavirus

For nucleic acid detection in novel coronavirus, samples were collected according to the "Sample Requirements" section of the kit instructions. Routine sample types include throat swab, nasal swab, sputum, bronchial lavage fluid, alveolar lavage fluid and so on.

After obtaining patient samples, it is necessary to test them as soon as possible. If the samples that need to be transported cannot be tested immediately, they shall be packaged at low temperature according to the requirements of the instructions and sent to a special testing institution for testing. After receiving the sample, the testing institution shall extract nucleic acid from the sample, and the nucleic acid extraction reagent shall use the nucleic acid extraction kit specified in the approved product specification.

Viral RNA needs to be reverse transcribed into cDNA before amplification and detection. PCR amplification and detection should use the fluorescent quantitative PCR instrument specified in the approved product manual. The Ct value of the sample obtained by fluorescence quantitative PCR can determine whether the patient sample contains novel coronavirus.

In the above process, the collection, storage and transportation of samples, the extraction and detection of sample nucleic acids and the interpretation of results must be carried out in strict accordance with the requirements of the kit instructions.