Reporter : Liu Runan / Publisher : China Science News
Ref : http://news.sciencenet.cn/htmlnews/2020/8/444671.shtm
Translation, editing : Gan Yung Chyan, KUCINTA SETIA
On 24 August 2020, a study by Yuan Guoyong, Academician of the Chinese Academy of Engineering and Chair Professor of the Department of Microbiology, Li Ka-shing School of Medicine, University of Hong Kong, and his team was accepted by Clinical Infectious Diseases and published online.
The study revealed the second case of a 33-year-old man in Hong Kong who was infected with SARS-CoV-2. The patient was diagnosed with covid at the end of March, recovered and was discharged from the hospital in mid-April, and went to the United Kingdom and Spain in August. He was diagnosed again when he was tested after returning to Hong Kong. This is the first confirmed case of covid in the world where a second infection has been confirmed.
How to determine that the man is re-infected? What does it mean to be infected again? Can the vaccine under study work? With these questions, China Science News interviewed relevant experts.
What is the difference between "fuyang" and "secondary infection"?
Jin Dongyan, Professor of Precision Medicine at the Huo Guangwen Foundation of the University of Hong Kong, explained that the academic community generally believes that after a patient has a negative test result and discharged from the hospital, he has tested positive for viral nucleic acid but has no obvious symptoms and there are antibodies in the body. This is "fuyang" ". "There is no live virus in the body, but when the body's immune system clears the infected cells, some nucleic acid fragments are detected, and its viral load is low." He said.
Researchers from the Department of Microbiology of the University of Hong Kong compared the genetic sequence of the two virus strains infected by the man and found that there were 24 nucleotide differences.
"His body's immune response is also different." Jin Dongyan told China Science News, "The man had no antibodies detected in his body for about 10 days after his first infection. In the second infection, he was only 5 days after admission. The antibody was detected and the titer was high. At the same time, the virus concentration was high on the first day of detection, and then dropped quickly."
Therefore, this is a re-infection after recovery, not "fuyang".
"There are many serum research results that show that within two or three months, the patient's antibody level will drop significantly. Based on this, we speculate that there will be cases of secondary infections. The cases in Hong Kong this time are definite evidence. "Liu Youning, chief physician of the Respiratory Department of the Chinese People's Liberation Army General Hospital, said.
Will secondary infections become the norm?
On 26 August, Zhang Wenhong, Director of the Department of Infectious Diseases at Huashan Hospital affiliated to Fudan University, stated on his personal Weibo that the identification of "re-infection" cases is a very important phenomenon, but it is still an isolated case. The reinfected case in Hong Kong shows mild symptoms when he was first infected, and his antibody levels at the time of discharge were unknown (more details after the publication of subsequent academic papers are needed), and their previous infection history still has a large atypicality.
If the case is a definite clinical phenomenon and becomes an index case in science, then more cases can be traced back to pandemic regions (Europe, America, India, Russia and other regions). In areas where cases are high, reinfection will become the norm and will be easily observed by subsequent cases.
Liu Youning said that in the future, there may be more cases of re-infection. "Among many infectious diseases, re-infection is a common phenomenon, and it is an individual phenomenon that can form lifelong immunity."
"In the coronavirus family, SARS, MERS, etc. have not been found to be re-infected. On the one hand, because the number of cases is limited, on the other hand, the virus does not exist in the environment. However, there are four types of coronaviruses that cause colds. Basically, there is no immunity and will be repeatedly infected." Liu Youning told China Science News.
He estimated that the human body’s immunity to SARS-CoV-2 lasts much longer than the cold caused by the coronavirus, but shorter than SARS and MERS.
Jin Dongyan believes that based on the results reported so far, this discovery is both bad news and good news. "The bad thing is that the antibodies of the infected person after recovery are soon undetectable, and re-infection occurs, and the re-infected individual is also very contagious; fortunately, the re-infected person is highly contagious for a short time, and after two days it has been greatly it is reduced, and it is symptomatic, and there is no serious illness."
Does the vaccine still work?
Jin Dongyan said that the location of the virus detected in the two infections was different. After the second infection, the virus concentration in the man's nasal mucosa was higher, but it was not detected in the lungs. "This shows that during the second infection, the body has a certain degree of immune protection, so there are no symptoms."
"At present, the most promising is the inactivated vaccine. Its effect of stimulating mucosal immunity to achieve a protective effect is very poor. It may not protect the nasal mucosa, and the possibility of re-infection is still relatively high." Jin Dongyan said.
"Our expectations for vaccines can be lowered. The first batch of vaccines that can completely prevent re-infection is of course very good. If re-infection cannot be prevented, it can prevent patients from becoming severely ill and prevent some people from being infected. This is also acceptable." he said.
Bloomberg reported on 24 August that Maria Van Kelkhoff, the technical leader of the World Health Organization's emergency project, said at a press conference that day that it is important to record cases like Hong Kong, but do not rush to conclusions. She said that long-term studies to follow a large number of cases are needed to better understand the strength and durability of the neutralizing antibody response of recovered patients to SARS-CoV-2.
Jin Dongyan also said that there are still many problems to be studied. She asked, "Why did the antibody level of this re-infected man decline rapidly during the first infection? What is the specific reason for the asymptomatic symptoms during the secondary infection?"
No comments:
Post a Comment