Many people are re-infected with Covid-19

HanoiOne month after recovering from Covid-19, 41-year-old Duy, with a mild cough and sore throat, tested positive for nCoV.

“I’m really confused, I don’t understand how I can get Covid-19 twice in a month,” he said. Only on the 23rd of Tet, he no longer had Covid-19 symptoms, his body was healthy. A few days ago, his wife and several of his colleagues tested positive. On February 22, Mr. Duy showed symptoms of fatigue, cough, sore throat, sore throat, no fever, quick test and PCR test results were positive. He thinks he may have contracted the infection again from his wife.

Ms. Ngan, 37 years old, living in Ba Dinh district, has a similar situation. She had recovered from Covid-19 at the end of January. On February 19, she had a sore throat, runny nose, and a quick test was positive. “This time the symptoms are milder than before, I have not lost my taste and fever,” she said, adding that a few of her friends have also been infected again since Tet.

Doctor Nguyen Huy Hoang (Vietnam – Russia Hyperbaric Oxygen Center, Ministry of National Defense), who treated these two patients, said that one day he consulted for about 100 F0, 5-10% of which were cured. , but tested positive again after 3 weeks to a month. The doctor said that these patients may be re-infected with a new strain.

Dr. Pham Van Phuc, Department of Intensive Care, Central Hospital for Tropical Diseases, also encountered a few cases of reinfection. The patients tested positive after about a month of recovery, their symptoms were milder than the first time, and were advised to self-isolate and treat at home, without requiring hospitalization.

Explaining the above phenomenon, Doctor Phuc said that after recovering from Covid-19, the body will produce antibodies to fight the invasion of nCoV. However, the amount of antibodies produced by each person is different, depending on the location, background disease… Therefore, if the antibody is not strong enough, the person recovering from the disease will subjectively not comply with 5K, when exposed to F0. Carry New strains will be at risk of reinfection. “For example, the first time the patient is positive, the patient is infected with the Delta strain, the second time can be infected with the Omicron strain,” said Dr. Phuc.

One hypothesis suggested by Dr. Hoang is that maybe the first time the test was negative, the patient took a wrong sample, or maybe nCoV is no longer in the nasopharyngeal fluid but still deep in the lungs. After knowing negative, the patient did not focus on health protection, the body weakened, causing the nCoV still in the lungs to work again, causing symptoms to appear and the test showed that it was positive again. This causes patients to mistakenly think they are reinfected, when in reality it is just a residual viral load from the initial infection.

However, with the current complicated epidemic situation and high infection rate, doctors think that there is a very high chance that reinfection will occur, when symptoms reappear and they are in the risk group (when surrounded by many relatives or colleagues with Covid-19).

“To be certain of reinfection, it is necessary to sequence the viral genome. If the viral genes are different, there could be one change in the genome or two different strains, and culture shows that the virus is still alive, then the person is certain to be human. This is re-infected,” said Mr. Hoang.

A doctor treats and takes care of people with severe Covid-19 disease at the Covid-19 Resuscitation Center located at Ho Chi Minh City Oncology Hospital, Campus 2, September 2021. Photo:Quynh Tran

Around the world, since the first year of the Covid-19 outbreak, scientists have discovered Viruses can cause reinfection. The first recorded case of reinfection was a 33-year-old Hong Kong man. He first got sick on March 26, 2020. 142 days later, he was re-infected with another nCoV strain.

According to British scientists, a person is determined to be re-infected with nCoV when testing positive more than 90 days after the last illness. UK Office for National Statistics (ONS) data offers a different definition. A person is considered reinfected if the test is positive 120 days from the last illness (or positive after 4 negative PCR).

Studies to date have shown that re-infections will be milder than those of the first infection, regardless of which variant F0 encounters. Even if antibodies are not strong enough to protect a person from a second infection, T cells (killer immune cells) prevent severe transfer and death. F0 rarely has serious symptoms. However, there is still a small percentage of patients who experience serious complications after re-infection with nCoV, this depends on the time of illness.

Reinfection will help strengthen the immune system in the patient. It acts as a booster dose of the vaccine. But the patient is still not 100% protected. Many data show that some people are reinfected more than twice.

According to the ONS, re-infection rate has increased 15 times since Omicron appeared. To date, reinfection cases account for about 10% of all F0 in the UK, much higher than 1% in November 2021. According to scientists, the phenomenon of reinfection is increasing due to community immunity weakens, no longer enough to prevent the virus. The appearance of new strains like Delta, Omicron makes it difficult for the immune system to recognize, the virus can evade. Besides, nCoV almost enters the human body through the nose and throat. This mucosal antibody tends to be relatively short-lived compared with systemic immunity. That is why immunity against severe disease, which usually originates in the lungs, lasts longer than immunity against infection.

Doctors said that the older the person, the background disease, the person with impaired immune function such as HIV, cancer, diabetes, chronic heart disease, organ transplant, the person who has not been vaccinated… higher reinfection.

Currently, the Ministry of Health has no statistics or reports on the rate of re-infected people. Around the world, some experts believe that reinfection cases of the same type of mutation are extremely rare. The phenomenon of getting Covid-19 twice with two different strains is thought to be more common. Research by Imperial College London shows that around two-thirds of the more than 3,500 volunteers who tested positive in January 2022 had previously had Covid-19. British health authorities in December 2021 estimated the risk of re-infection with Omicron to be 5.4 times greater than that of Delta.

To prevent Covid-19, including reinfection With new strains to protect people in high-risk groups, Vietnam and many other countries have deployed the third dose of vaccine. In addition, doctors recommend people to strictly follow the 5K principle, especially wearing masks, washing hands often, and limiting touching your eyes, nose and mouth, even after recovering from the disease. Eating, living scientifically, getting enough sleep, drinking plenty of water, regularly exercising, are effective measures to improve resistance and prevent re-infection.

Thuy Quynh – Thuc Linh


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