15-10-2020 by Mirai
Immunization against Covid -19 still raises many questions. Dutch researchers have just reported the first case of death after a reinfection with Covid-19 in the journal Clinical Infectious Diseases.
Once cured of Covid-19, is it possible to get infected again with the coronavirus? Researchers have notably studied the case of a second time infected with SARS-CoV-2.
It was an 89-year-old woman who suffered from Waldenströms disease, a form of blood cancer. The patient first presented to the emergency room with a fever and severe cough, before testing positive for Covid-19. Five days later, she was able to return home because she no longer showed symptoms other than persistent fatigue. Fifty-five days later, and two days after chemotherapy, she again developed a fever, cough, and shortness of breath. A PCR test was done again, which came back positive. She also underwent a serological test, which in turn came back negative: she had not developed any antibodies against Covid-19 and therefore could be re-infected with the virus.
Five cases of reinfection in the world
In another study, published in October in The Lancet Infectious Diseases, researchers also looked at the case of a 25-year-old American who was twice affected by the new coronavirus. In mid-April, the young man presented mild symptoms of the coronavirus. In particular, he had a cough, headaches, and diarrhea. Towards the end of May, the patient was experiencing severe breathing difficulties and was admitted to the emergency room where he was administered oxygen. After a new PCR test, he was declared positive for Covid-19 a second time.
A genetic analysis revealed that the patient was infected with two different strains of the new coronavirus. "There are still many unknowns about SARS-CoV-2 infections and the immune system response, but our work shows that a previous infection may not necessarily protect against a future infection," said Professor Mark Pandori of the University of Nevada and lead author of the study.
Since the beginning of the epidemic, five cases of reinfection have been confirmed in Hong Kong, Belgium, the Netherlands, Ecuador and the United States. "That does not mean that there are not more, especially since many cases of Covid-19 are asymptomatic," said Professor Pandori.
Covid-19: a patient tested positive twice, almost 5 months apart
Last August, a first proven case of reinfection was reported in Hong Kong. In one study, published in the journal Clinical Infectious Diseases, scientists were interested in a 33-year-old man showing symptoms of the disease and who tested positive for the coronavirus on March 26. After his recovery, he tested negative twice. But on August 15, four and a half months after his first infection, the patient tested positive again at the Hong Kong airport, despite showing no symptoms.
The researchers say that genome sequencing shows that the two strains of the virus are "clearly different." That is why this patient is considered the first proven case of reinfection. But other specialists prefer to interpret this finding with caution: "It is difficult to draw definitive conclusions from a single case. Given the number of infections in the world, seeing a case of reinfection is not so much." surprising, ”said Dr Jeffrey Barrett of the Sanger Center (UK), for example.
Coronavirus: do cured patients still carry the virus?
Before this patient, other cases of possible reinfection had questioned scientists. Next, several hypotheses were raised.
Were patients who recovered and then tested positive re-infected, or did they still carry the virus? "I am not saying that reinfection cannot and never will, but in a short period of time it is unlikely. Even the mildest infections should leave at least short-term immunity to virus infection in the recovering patient." explained Florian Krammer, a virologist at the Icahn School of Medicine at Mount Sinai (United States), in New York.
Opinion shared by Dr. Marina Karmochkine, doctor in clinical immunology at the Georges Pompidou hospital in Paris: "The antibodies conferred by this infection will have a protective capacity, undoubtedly for a few months," he explains to BFMTV. However, she pointed out that this protective capacity is not the same as that obtained with a vaccine and that it was still too early to have enough perspective on the matter.
Covid-19: failed tests?
The explanation for these cases that tested positive several weeks after their recovery could be quite different: Some experts also suggested that the bodies of these patients still contained a small amount.virus that the tests could not detect.
The coronavirus diagnostic test involves removing cells from the back of the nose with a swab. Part of the genetic material of the extracted virus is then amplified using a technique called PCR, which allows it to be better detected.
However, "a negative test does not mean with certainty that there is no more virus in this person," recalled Marc Lipsitch, an epidemiologist at the Harvard TH Chan School of Public Health (United States). The question? The target area of the sample, which may not contain virus at the time of testing, or storage of samples at an inappropriate temperature, which can cause deterioration of the virus.
Sars-CoV-2 virus: hypotheses to be taken with caution
Likewise, the positive tests of patients several weeks after their recovery may also have another explanation: a study published last February in the Journal of the American Medical Association (JAMA) indicated that four patients with Covid-19 who responded to criteria for the They were discharged from hospital and who no longer showed signs of infection, had tested positive for the virus between 5 and 13 days later.
These explanations are still only hypotheses, the precautionary principle is valid. To limit the risk of contamination, it is recommended:
Wash hands frequently;
respect social distancing;
coughing or sneezing into the crook of the elbow;
use tissues;
Wear a mask.
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