Coronavirus. What the new studies on asymptomatic and immunity say

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Recent studies on coronavirus change paradigms and raise questions about the evolution of the pandemic in the context in which relaxations and vacations have led to an increase in cases of Covid worldwide, but especially from the perspective of a second wave in autumn and reopening. schools. The new studies therefore focus on the most controversial issues of the moment: the transmissibility of the virus by children and adolescents, asymptomatic vs. symptomatic and immunity to Covid 19.

The best example is a study done by American researchers who found in children under 5 years of age an amount of virus 10 to 100 times higher than in adults in the upper respiratory tract.

The study, published in the pediatric journal JAMA Pediatrics from the United States, aimed at analyzing 145 samples collected in March-April from patients with moderate symptoms, one week after their onset. 46 of them were from children under 5 years old, 51 from children between 5 and 17 years old and 48 were adults between 18 and 65 years old. However, the mentioned researchers did not study the transmissibility of the virus.

An analysis made by Russell Viner of University College London suggests that young people and children have played a much smaller role than adults in the spread of the virus in the population, as confirmed by a study by Australian Committee on Health Protection (AHPPC).

Russell Viner’s research shows that adolescents and children under the age of 20 have 56% less likely than adults to become infected when they come in contact with a person with Covid 19.

The coordinator of the study by the Americans, Dr. Taylor Heald-Sargent, claims that these findings will help establish new rules. in schools and kindergartens, such as increased attention to lack of personal space, children’s hygiene, their play or wiping the eyes and nose. Preventing the spread will be difficult, but it is important that this happens.

“It’s a chore to make them wear a mask, wash their hands and not put anything in their mouth or nose. However, adults who have appropriate behavior can become a role model for them, “said the doctor.

Symptomatic and asymptomatic

A study conducted in February on an outbreak of a religious group in Daegu by researchers at Soonchunhyang University, South Korea, and published by the American journal Jama Internal Medicine, to miss that 29% of people infected with coronavirus never had symptoms, but carried the same amount of virus as symptomatic peoplee. However, finding residual viral particles in the nose, throat or lungs does not necessarily mean that these people have been contagious. Hence the big question of the pandemic: how many asymptomatic cases are vectors of the virus and how dangerous are they when they come in contact with other people?

The study, led by Professor Seungjae, focused on a focus of the Daegu religious group of 303 people, with positive cases with few or no symptoms placed in isolation, where doctors and nurses meticulously monitored their symptoms and tested them. viral load on a regular basis. Out of 303 people, 89 never showed symptoms, a proportion of 29%.

“It is important to emphasize that the detection of viral RNA is not synonymous with the presence of an infectious and transmissible virus,” warn the study’s authors.

UAnother study by eight Chinese researchers shows that asymptomatic people do not transmit the virus. The research is extensive: of 455 people who came in contact with a person tested positive for Covid, but asymptomatic, none contacted the virus. They were monitored and monitored for five days, and all PCR tests, CT scans and blood tests denied the presence of the virus. Of the 455 people, 25% had cardiovascular disease. The research was indexed by National Library of Medicine and sent to the World Health Organization (WHO).

On the other hand, the doctor William Hillmann of the Massachusetts Hospital, he said in April that “o a significant proportion of people who are completely asymptomatic are contagious for a period of time. ”. World Health Organization he now argues the same thing, which is why social distancing became essential. So is large-scale testing.

Asymptomatic people quickly lose their immunity

A team of scientists from the University of California, Los Angeles, USA, conducted a study, published in The New England Journal of Medicine, on a number of 34 people with mild symptoms of Covid and who have recovered. Conclusion: Every 73 days, the levels of antibodies – proteins produced by the immune system, which prevent viruses from infecting the body’s cells – have halved.

The researchers tested the subjects’ blood two or three times over a three-month period. The results highlight fears that immunity to SARS-CoV-2 may not be lasting in individuals who have had mild symptoms, which make up the majority of people with SARS-VOC2, the study shows.

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