Why do some people "revert to positive" after COVID-19's nucleic acid test turns negative?

"After being infected with COVID-19, a few people may still be infected with the variant subtype of Omicron again." 65438+February 65438+June, Zhang Boli, an academician of China Academy of Engineering, said that through the observation of Omicron epidemic at home and abroad, it can be concluded that COVID-19 is still mutating and has strong immune escape ability.

"There are many subtypes of Omicron strains that are popular at present," Zhang Boli said, so it is difficult for human body to establish a comprehensive immune barrier against different subtypes of Omicron.

In addition to BA.5.2 and BF.7, which are widely spread in China at present, the mainstream subtypes in other countries are BQ. 1, BQ. 1 and so on.

Academician Zhang Boli reminded that the variation of virus will reduce the specificity of neutralizing antibodies produced by different subtypes of infection, and antibodies will intercept and mutate into new subtypes.

There are still symptoms after turning negative. What should I do?

In the past week, the number of infected people in COVID-19 has increased significantly. According to the current clinical experience, the course of most infected people is about 7 days. If there are fever symptoms, most of them will recover after 3 days. People who have been vaccinated with COVID-19 vaccine and completed intensive immunization have a shorter course of disease and a lighter condition.

However, after the nucleic acid or antigen test turns negative, some patients still have symptoms such as cough, sore throat, fatigue or loss of appetite. What should I do?

For patients who still have mild symptoms after recovery, Zhang Boli suggested that after the nucleic acid turns negative for 2 days, the body temperature should be kept normal, and the rest symptoms should be obviously relieved before returning to work and study. Elderly patients with basic diseases can rest for a few more days.

For those infected people who have no obvious symptoms, but just recovered soon, Zhang Boli also reminded that Chinese medicine stresses "prevention of disease", that is, when the disease has just been cured, the vital qi in the body is still weak and the body function has not fully recovered. At this time, we should also pay attention to the conditioning after illness, on the one hand, consolidate the curative effect, on the other hand, prevent the recurrence of the disease.

Why is it "Resurrection Yang"?

● Ms. Xia, who lives in Henan, said: "On February 7, 65438, I did an antigen test at home and the result was positive. After family treatment, the antigen results of 10 were negative for two consecutive days after the symptoms disappeared on February 9. However, in June 5438+February 65438+February, due to symptoms such as fever and cough, the antigen was tested again and the results showed positive. "

● Ms. Cui, who lives in Beijing, said: "On February 8, 65438, the day after I had a high fever, my antigen test was positive. In February 10, there was basically no fever. After the antigen of February 14 turned negative, it began to have a low fever today. "

An infectious disease expert at Shanghai Changhai Hospital said that Yang's recovery needs to be confirmed by nucleic acid testing. The so-called "positive recovery" does not rule out the existence of false positive or false negative self-test antigen; In addition, if the nucleic acid test results also show abnormalities, it does not mean that the disease has recurred, it is likely that it did not recover at the beginning, and the antigen may be false negative.

In Ms. Xia's case, the infection in the same residence will inevitably lead to the spread of the virus in the living environment. At this time, the antigen results of people living in the same living environment may be false positive.

Similar symptoms appeared after Ms. Cui's antigen was negative. It is not excluded that the patient is still in the course of the disease. At this time, the viral load is lower than before. Because of the sensitivity of antigen detection, the result is false negative.

Is Fuyang contagious?

It should be noted that recurrence and reinfection are two different concepts. The former is that the infected person has two positive results in the same infection cycle, and the latter is that the infected person has experienced different infection cycles.

Zhang Boli gave two possible explanations for Yang's recovery:

One reason may be that antigen testing gives false negative results;

● Another reason may be that the virus fragments brought out by phlegm thrombus are positive.

"The antigen detection speed is fast and the operation is convenient, but generally only when the virus replicates to a high level and the infected person detoxifies a lot can the antigen be detected." Zhang Boli explained that due to the low viral load in the late stage of infection, false negative results may appear in antigen detection, so it is generally recommended to self-test antigens for two consecutive days, or take nucleic acid detection as the judgment standard.

"In addition to excluding misdiagnosis and false positives, there is another possible reason related to the patient's phlegm." Zhang Boli told reporters that due to the sticky sputum thrombus, the sputum thrombus was wrapped by virus, and the recovered people brought out the virus when discharging the sputum thrombus in the subsequent lung repair process. At this time, the virus nucleic acid fragment is positive, so it is impossible to cultivate a live virus.

Zhang Boli stressed that no matter what causes the recurrence, it has been confirmed by clinical observation that it has not infected others.